Idle Time

Just out of curiosity, while typing a long post, forming a large thread, or when merely stepping away from the computer, how long can I remain 'idle' until getting automatically signed out?
Luckily, by learning from past mistakes, I have learned to copy all posts when finished, so as not to risk losing the whole post, if signed out; but I would love to know the time limit, or an estimation.
Thank you! :)

I think it is 15 minutes, mono.

Cookies should keep you signed in indefinitely if you use them, but I've had problems in the past on other forums using the same software so on long posts I crtl-a ctrl-c as well.