Once upon a time, I did this with DC. So many Batman/Flash/GLC figures in Mini-Mate, 3" PVC, 3.75" DC Direct, 3.75" Mattel DC, 3.75" GL Movie, 5" JLA/TJ, 5" Super Powers, 6" Mattel, 7" DC Direct. Lots of different lines, lots of different scales.
When DC wiped out the Silver Age continuity and origin stories and rebooted with the new 52 and all that, my interest died. The stories got too far from what I enjoyed (they erased Wally West! Too much Damian Wayne! WTF did they do to the GLC?) I just lost interest in the new stories they wanted to tell. I stopped buying the comics and then stopped buying the figures.
Almost all of my DC/GL stuff is gone now with the exception of a "classic" 3.75" scale Hal Jordan and my Power Ring/Battery (still love that thing). I still have some 7" figures and some other 3.75", but they've been stored in baggies, off-display, and destined for the "for sale" bin for a while now.
Even within Star Wars, I've been asking myself "how many Darth Vaders is too many?" I've been culling older versions for a while now, really trying to stick with "if I can't display it, I don't need it". When I get a new Vader/etc, I try to think if I can retire an older sculpt in its place and make some room/money so the cycle of rebuying can continue.
