I lost both of the twin spot gobies I bought. The first one went just about a month after I got them, I think stress did him in. The second one lived for about 6 months and died just recently. They're not great eaters of frozen stuff. The one that lived longer ate reasonably well, but obviously not well enough. I can't believe he starved to death when at night with the flashlight I watch all the stuff running around on the gravel and rocks. Oh well.
My daughter thought she'd get me a nice B-day present about a year and half ago, a cute little spotted box fish. But she bought it from a bad LFS and it died of ich (thank goodness I had my smaller tank at the time and it wasn't reef, I could treat the other fish who did get it also).
And I lost Tiny Tim. (Klein's butterfly), who I set up a special tank for. he was doing great. Thought I'd get him a buddy. The 'buddy' is now nicknamed "KILLER". You get the picture.
Otherwise my other fish have all been around for over 2 years. My yellow damsel, "Rudy", who was one of the "cyclers" for my first tank is now almost as big around in his body as my sailfin tang.