As much as I can and have money for(feel like spending money on).
Last year, or cosplay season (which I count one year from the biggest con I'm attending. So A-kon.. my cosplay season started last year June and ended this June. I start on new cosplays), it was my first time getting back into cosplay and con after a 6 year break... Before I simply didn't have rides or friends to accompany to go to cons that I wanted to, even if they were really close :/
I tried to go to a few cons during that season, but I always didn't have someone to go with, and I felt too shy at that moment to go alone. Missed out on alot. lol So A-kon 23 was my only con for that season.. and after I finished that one I realized I wanted to do this alot more often!
So this "season" I'm hoping to go to at least four (one ABOUT each real
season (like fall, winter, spring). To get my fix XD). Six if I have the funds and time to request off.
EDIT: I would agree that "too much" is really up to you.. to be honest. To me, too much is when you're constantly going broke JUST to go to every convention there is. Conventions are a little expensive, especially out of town ones. And if you're running yourself ragged trying to go to all of them. But even then.. if you're enjoying yourself and you're happy, "too much" is relative