Forum timing out

[Phoenix]

I read the forum primarily at work.  There are times when I pull up the forum and then get busy with work and am unable to return to the forum for 30 minutes to an hour.  By that time the forum has timed me out (for a lack of a better term) and set all the threads to read.  Is there a way for me to extend the default timing?  I looked around in my account setting but didn't find anything.