I always get my partner at the time a card and a gift to mark the date but I don't find first years all that special. Especially when I've had quite a few by this point. I usually get bored around the 2 year mark and very unexpectantly drop my partner which is something I'm trying to work on doing less.

Most of my partners have found first years special and insisted on the dinner/date thing, which is nice but not a necessity. Five years is a little more impressive; not many couples seem to reach five years these days, myself included.

I'd say 50 years is a good time to celebrate. Or 50 sexual partners. Whatever floats your kinky little boat.