First, you should remove this timeout. This is the
authenticaion timeout (how long someone's login session is valid, either rolling or absolute). This is normally set to 20mins, and if it expires the user will need to be re-directed to the login page if they try to access something secure.
You are getting an execution timeout, you can extend this (see
this[
^]) *BUT* you are better off optimising the long running process that is causing this. A typical example would be an SQL call that isn't well written and therefore taking a long time.