I am actually at the same point with collecting; I have almost every game I ever wanted since I started back in 2008 and then some. I used to hunt for games almost every day, now, for a variety of reasons, I buy most of my games on Ebay since it is often easier and typically cheaper since all, but a few places I used to hunt have dried up or are so saturated with collectors and resellers you have to be very lucky to find anything. The collecting landscape has changed dramatically in the past 2-years alone and it is a far cry from the highly accessible and highly rewarding scene I started in. So part of my plateau is the fact that running around looking for cheap games has not only become mostly pointless, but it has lost most of its appeal to me.
But despite this, I am grateful I started before the hobby got as big as it did and was able to get most of the must have games on all the retro consoles I had an interest in. The only older consoles I still have a sizable log of games I would like to get are ps1 and Saturn. I have most of the N64 games I've ever wanted, but one thing I've been gradually working on is getting all my childhood games CIB. I'll also note that I have been collecting pretty aggressively for the PS3, 360 and Wii, but that is just because games on those consoles are becoming more and more common and are dropping in price like crazy.
But yeah, my intake of games has dropped pretty dramatically and it is near the point where I'm not sure I'd be able to amass more than 100 games this year. It's sad in a way, but also a bit of a relief.