You're young yet.
Since your collecting is really a "store of value" and not an expense, you have low risk in continuing to acquire, and plenty of time to decide when to begin culling. As "cussedemgun" indicated -- you may very well eventually shift your interest, resulting in a natural change in your acquisitions/disposals. You may also shift toward improving your collection, rather than increasing its volume.
From my experience, as your collection grows and you get (significantly) older, you will begin to think about your own mortality -- and its impact on your collection (among other things). There comes a point when you try to balance your ownership of material things with the idea of eventually having someone (your family/children/heirs) either inherit your belongings or having to dispose of them for the benefit of your estate. Realizing they might be burdened with stuff you enjoy but they might not, you tend to taper off your possessions as you approach your later years.
In my younger years, I was mostly constrained by space. Eventually, I used the excuse that I had to get rid of something in order to acquire something else in its place. Once that ice was broken, I had an easier time of culling items from my collections. So, now at 60 I still don't fully heed my own advice -- but I'm working on it. I need to remember that I'm on the "downhill" side and need to improve rather than add.
The bottom line -- you've got a long way to go enjoying the building of your collection before you need to think that "enough is enough".
Just some late night thoughts...
Hope it helps.
Fred
the past month, unless you bought gold. Now, how much did the value of your firearms decrease? 
