i've got over five days and i can tell you over four days of that is the fact that i use firefox, so i'll leave getbig on one tab that sits there for hours at a time even when i'm not in the house. online time hardly means anything.
There is a misconception here that when you've finished "downloading" a page on getbig that mystical contact is still happening behind the scenes. A browser inteprets code for a page and then displays it. Very few pages run background applets to maintain connections and you wouldn't do it on a forum because it would cost you a lot of server power to do so (1000 concurrent connections refreshing logins - I think not

).
Firefox doesn't reload getbig (getbig does not request automatic reloads) or as far as I know make any sustaining contact to getbig when it is idle so that theory is probably false.
Just to give you an idea - for the entire time I've used getbig it has been on firefox (and its previous name) and I have been mostly unemployed during that time with getbig loaded. My online time doesn't touch a lot of people here.
As I've said several times here, the time online function is almost certainly an amount of time incremented onto your time online everytime you refresh a page (that is, everytime you refresh one and a login is performed). The reason I say this is because the system tracks how many people are online at one time which is actually just how many people have logged in in the last 30/60 mins.
So if you check getbig every 30 mins to 1 hour you will get a huge time online figure. But its not accurate atall.