Howdy eb07.
I've been carrying and using revolvers for a while, and I developed my loading (reloading
is loading

) skills back in the days of carrying issued service revolvers (K and then L-frames). We generally didn't get down to specifically timing the loading manipulation itself, but required that shooters be able to load as necessary within a time limit for any particular drill/qual scenario.
For example, one of the qual requirements at 15 yards was to fire 6 rounds at a bulls-eye (2-handed, but you could shoot 1-handed if you thought you were cool and skilled enough), then load and shoot 4 more rounds, in no more than 25 seconds, total. Generous timing, right?
Well, the 4 rounds could be loaded loose (bullet loops, dump pouch, from the pocket) or from a speedloader (but which had to hold only 4 rounds), and naturally part of the skill needed was to index the cylinder when closing it so the next round up with the DA pull was the first of the 4 fresh rounds. The guys using bullet loops (or pockets) were slower than those of us using down-loaded speedloaders.
In subsequent days of semiauto pistols having replaced revolvers, the usual reload/load time allowed is usually a comfortable 4-5 seconds. That may seem like a long time, especially when skilled guys & gals can replace mags in 2 seconds or less, but things can get fuzzy and fumbly when the timer is running and you're not standing in the exact upright and comfortably balanced position you like to use, and as a result your hand isn't finding the mag carrier as easily. Toss in some movement and some minimal range stress (and we're not even talking Simunitions or force-on-force training) and fingers get all kinds of fumbly.
I still use the same Comp 1 or 2 & HKS speedloaders for my J's I used for them, and my other larger revolvers, in the older days. Speedstrips, too. Mostly speedstrips, as a matter of fact, simply because they're easier to carry.
Rather than worry overly much about "speed", I tend to focus more on smoothness of manipulating the revolver and whatever loading system I'm using at the time. I like to switch back and forth between speedloaders and speedstrips during range sessions, but also still use loose rounds (when time constraints permit), if only to make me focus on retention of the involved, trained fine motor skills under normal range stress conditions. Use it or lose it.
I don't see quite as much "need" for blazing fast loading when I'm carrying one of my J's. I'm not typically carrying one of them in the sort of environments where I anticipate extended round count and loading speed to be a highly probably issue. I carry extra speedstrips and speedloaders for my J's in the hopefully rare event I may need to load during a lull/cover situation before the local cavalry has had time to arrive. Also if I'm going to be traveling away from home for any length of time.
Then, of course, there's the ingrained habit of earlier years to carry 2 extra cylinder loads, since that's what we did for duty.
If you can load your 5-shot snub, while remaining behind cover, crouched or are moving to a better spot, while remaining aware of the potential threat(s) around you, and successfully close/index the snub cylinder, while maintaining a proper grasp on the snub and control of it ... I'd not lose sleep if it was taking 4 second or 8 seconds, etc.
Getting it done
right the first time is the key. It takes a lot
more time to realize when something
wasn't done right the first time,
and then figure out how to correct it. That's the real time-killer.
I've also noticed that some of the newer S&W grip stocks aren't quite as friendly to some speedloaders as we might wish. Well, in the old days we usually had to have the wooden L/stock panel relieved to work with any speedloader, and it was a big deal when the rubber stocks, or custom "combat" wooden stocks, were advertised to be relieved for speedloaders.
FWIW, I don't use the 2/space/2 speedstrip method. I load my 6rd speedstrips with 5rds. Those strips are hitting the ground after I fill a 5-shot cylinder, so any 6th round in a 6rd strip is probably going to become part of the scene's evidence before it's actually used.
If I need to load less than 5 rounds, for some supposed situation where sheer speed is more important than loading all 5 rounds? Well, I can always drop the strip after loading 2 or 4 rounds, right?
Whatever you decide works best for you, just make your informed decision for whatever you use actually lets things work for you, under realistic conditions.
Nobody can tell you how fast is going to be fast enough, for either loading or shooting. (Or even becoming aware of an actual situation in enough time to even draw/present a weapon.)
Work your skills until they're smooth and fumble-free, and then keep testing them in different situations. One "sticky" empty case, or a case which hangs up against a rubber grip stock, or a cylinder which slips in your grasp and partially closes (preventing a case or 2 from fully falling free) ... can make everything seem much more difficult, regardless of how cool your speedloader is, or how fast you grasp it from your belt or pocket.
Oh yeah, my LCP's? Those really short and thin grip frames make inserting and properly seating a magazine a really deliberate effort. It takes a significantly different grip and manipulation to insert and seat a LCP mag, with the slide closed or even locked open, than it does with any of my other myriad pistols (subcompact to full-size). One of the disadvantages of the diminutive size of the LCP, and its
really short grip frame,
for me.
While I often carry a spare mag for one of my LCP's (depending on the size of the pocket in which it'll rest), I realistically don't anticipate having to load under the same stress and time constraints as I still train to do with my larger pistols, or even my J's.
My LCP's are one of the little guns I pocket (holster) when my activities and travels aren't going to be taking me places where I expect the sort of potential threats to exist where I'll need to have a gun. I sort of think of the LCP as being a "step down" from my J's, but still hopefully "enough" to deal with an imminent threat of serious bodily injury or death presented by 1-2 persons who aren't toting long guns, involved in active shooter situations, etc.
Sorry for the ramble, but I'd not really get too wrapped up around the axle about trying to nail down and really narrow down (re)loading times for the J's, even if carried as "primary" dedicated defensive weapons. Being able to deftly and smoothly load is a laudable goal, though. Trying to split hairs between a couple of seconds? Not so much, for me, at any rate.
If I were once again carrying a service-size 6-shot revolver, constantly putting myself into Harm's Way working as a full-time cop again, I'd want to make sure my (re)loading skills were polished so I could manage it in a couple seconds or less, using speedloaders in an exposed speedloader carrier that allowed for rapid and easy grasping. Off-duty? I'd be fine with a little slower times using smaller speedloaders, and even a bit slower for using speedstrips.
Fast and fumble free (re)loading while standing comfortably on the shooting line is fine, but can you do it while shaking and having sprinted 15 yards to hunker down behind something that's more
cover, than
concealment?
How well and fast can you actually shoot the little J's, though? That's probably a better, more relevant question to consider. Even the snub revolver drill commonly described as firing 5-shots, at 5yds, in 5 seconds and maintaining a 5" group, may give you some insight into your skillset, and where it might benefit from some polishing. If you're limited to a maximum of a 5-shot on-board ammo load, the accuracy and timeliness of those first 5 shots may be more important than the (re)loading.
Another drill I often use to 'spot check' myself, done 'cold', is a 1-handed, close combat/hip level drill with my J's. I usually do it at 2-4 yds, looking to make no larger than a tight fist-sized group, in an
intended area of the threat target, and preferably in 3 seconds or less.
Just some thoughts.