I go through at least a chunk of my collection every couple of weeks, just as part of the process of putting away new acquisitions or taking out/putting back games im playing. And honestly? Every so often I really do just pull them out to look at, for fun- I like just seeing all the pretty box/label art, remembering the game and/or how I came to own it, etc.
I'm rarely caught off guard by what I own, although I did once have to pull out the PS1 boxes to check on a game, becuase I was cleaning up my photo files & found a haul pic from a con with Ogre Battle in the shot, and I'd 100% forgot buying it. So I got to be happy twice, once when I bought it & again a couple months later remembering I did!
As for doubles- amazingly not an issue! I can only think of 2 times total where I bought a 'double without knowing it. The first was years ago, when I impulsively grabbed a Burgertime cart, only to discover I already had one in the Intellivision set. Of course, in my haste I'd bought a 2600 copy anyway, so I just started buying Burgertime variants to be silly. It's lead to my only legally licensed Chinese import, so ended up being a good thing! The second one was just recently- Devil May Cry 5 went on sub-$20 sale. I kinda thought I had it but wasn't sure, so I checked here- nope, not in the collection, I'll buy it! Then when it came & I went to put it away, I found out I had the Deluxe Edition & that's why it didn't come up when I searched it. Whoops- teach me to shop fast on break at work! Luckily it was an Xbox One copy, so I could give it to my brother (who was quite happy to have it!) Didn't seem worth the hassle to set up the return.
