Extended Time Out time or option to NOT time out

Our browsers time out after only 3-5 minutes. We bill our tasks in 6 minute increments, so every time we go to enter a slip, we have to re-login. If we are working on a project and have begun to enter time, then it logs us out, we lose what we had already entered into the slip and have to re-enter. We would like an option so that it does NOT log out