I check it whenever I'm slow at work and during lunch. Sometimes I just keep it open in the background when I'm working (I'm on e-mail basically all day long anyway). I don't always reply on posts but I do a lot of reading.
I'll admit that sometimes it is in search of misinformation to correct, but I am happy to say that that is getting to be less and less often (unlike some boards).
There are days when I check 5 - 6 times per evening and days when I do not check at all. Depends when I have time or if I posted something and waiting for replays. The search intensifies if I need information.
Since I got this app on my iPhone, I've been on about 5-7 times a day. Pretty much anytime I take a break, or lunch, at work. Then when I get home, I find that I keep checking using my phone, rather than turning on my computer. Just easier to use my phone.
I check at least once a day. I'll be honest and say that it's not because so much of the information is of interest. It's actually because there is too much traffic on this board and the New Posts function resets before I can scan through the posts I am interested in if I leave the gap between visits longer than 1 or 2 days. Today there was 5 pages of new posts since yesterday's visit! Great to see the forum thriving but I wish this forum had a 'last 70 posts' tab like Orchid Geeks... maybe it would need to be 'last 700 posts'.