Well, lets do it the long way. To answer your question I have two mIRCs (one is a hardcore bot) running 24/7 all year. I'm probably infront of them maybe ahhhh 8 - 9 hours a week...
I'd say 4-5 hours during the week (work interferes with chatting ) and 6-9 hours on a weekend, depending on who's around. And depending on my social life - wait, IRC is my social life! Sad huh? lol