I keep track,-- sorta. Every gun has its own file folder, with receipts, etc., which pretty much documents the history of that firearm with me. This comes in handy when selling or trading the gun. I keep the required bound book for C&R firearms, plus I keep another similar book for non-C&R firearms on the theory that it is a good thing in case of insurance claims or other situations that might arise.
I also keep a little notebook for each rifle, where I make a short entry for each time I do something to or with the rifle. This includes range sessions, adjustments made, accessories added, and rounds fired. Many times I have gone back to check something in that history, so it's worth the (very small) effort to me to keep it. I don't keep those records on pistols and shotguns, though.