The site is configured to do this after 1 hour of inactivity. If you happen to be creating a post and have that window open and typing in it now and then for over an hour you will be logged out as that is perceived as inactivity.
I've had the same report from one other person and have been looking into why this is going on but as it is so infrequent I've been at a loss as to finding the source. I'm wondering if there is something with a certain ISP as both of you are located in the same region. Please PM me with your ISP info.
While this is not at the top of my priority list I am actively looking into the issue.
