"one can spare themselves a ton of wear and tear by only firing a couple cylinders during a practice session, and using .38s for the bulk of the time on the range"
This can be a very bad idea,,,,, under Santayana's admonition "He who ignores history is doomed to repeat it".
The CHP troopers killed in the Newhall fight trained with .38s but carried magnums on duty, they achieved a 0% hit rate in that fight with their duty revolvers and this inability to hit the bad guys (among other things like bad tactics) cost them their lives.
The double edge to this sword is guys like Bill Jordan, but then Bill fired hundreds of thousands of .38 rounds per year building up his skills. Most of us can't really afford to do that without official assistance.
If you are going to train with .38s, then you need to end your training sessions with a couple of cylinders full of your carry load, or an equivalent load recoil wise.
Frankly, I think there is little reason to use full house magnums out of a K frame, the cost benefit ratio as far as stopping power vs recoil/blast/gun wear just isn't worth it, but then, it's your gun, do what you want with it.
Just remember, not only does the rule "only hits count" apply, but in real life only really good hits count, misses and/or shooting them around the edges a bit counts for nothing.