Kinda hard to put an exact number on it, since it kinda varies, but I'd say at least 3 times a day. I usually check it early in the morning, to check for PM's, reports, moderated threads, or anything that might need my attention right away. Once I'm done with that/if there isn't anything, I'll usually browse around for a while, before getting off and getting ready to go to school :p Sometimes I'll check on during school, but that really depends on whether I have the time or not, and it's usually just to check for any notifications.
I'll usually get on again once I'm home, which is usually anywhere between 2 pm and 5 pm, and from there it'll be kinda on and off activity for the rest of the day to be honest, but it's usually anywhere between 2pm and 12am I'll be posting around and stuff. But since I usually check on regularly in that time period, it's kinda hard to give an overall number for how many times I check PC a day, but yeah, I'm still on it quite a lot :p