I promised myself I will not allow it to go into the quad digits, ever. Ideally try to keep it under 500. The problem is I basically want any game that appeals to my interests, good, bad, obscure, popular, doesn't matter.
What I do when I have the time is go online and comb through each console library to try and educate myself as to what's out there and how hard it is to get. I've done this with most consoles is the reason why my list has got a big number. Some I still haven't, like SNES, SMS or Dreamcast, my knowledge is still very shallow on those. They will eventually bump the number up I'm sure.