If you are doing this for a while, you will likely develop very specific tastes. Perhaps Lew Horton interests you, 5 screws, rare or uncommon variants; something, after seeing a million model 15's, model 14's, 29's, etc., again, something will stand out and be of specific interest to you.
When this happens, you may wish to buy multiples of the same variant, regardless of cost (ouch!) or the time it takes to find them--as a collector and shooter.
My current school of thought on the NIB: I will keep them this way until I retire....then shoot them and enjoy them. I'll want a LNIB or NIB variant and won't be able to find it. No worries, I got a new one and could care less if it goes down in value a bit as a result.