Quote Originally Posted by vladsch
Just remember that it is not inactivity of the computer keyboard and mouse but the web application....
Of course. Here's a quote from the forum software's support forum:
When you log in, vBulletin writes a cookie with an expiration equal to the cookie timeout unless the "Remember Me" checkbox is checked. This cookie gets updated every time you load a page, because you essentially login on every page load. So you can have your cookie set to the default (15 minutes) and browse the board for an hour without issue. Then you read a long page, get up and get a drink, and as time elapses the cookie expires. Bam you were "randomly" logged out.
Do you have "remember me" checked? If not, try it to see if it makes a difference.

As to changing the timeout value... based on what I was able to find it appears there are two camps; one group pushes for short (15-min or less) and the other for 1-hour. Seems that once it gets below 15-min/larger than 1-hour the user complaint level goes exponential. How busy the forum is and your personal browsing style tend to drive your desire to have it one way or the other. Unfortunately, there's only one timeout value per site, not one per member.

BTW, I'm going to move this to the "Site Comments and Suggestions" forum... the nature of this discussion seems to better fit there than in general razor discussions. Hope that's ok?