Hello,
You cannot disable timeout in the current version, however you can increase timeour period.
1. Go to the [%SB_DIR%]\Web\Web.config file.
2. Find 'roleManager' tag, change it's 'cookieTimeout' value (in minutes).
3. Find 'sessionState' tag, change it's 'timeout' to the same value.
4. Find 'forms' tag, change it's 'timeout' to the same value.
It should help.
Warranty: this changes aren't supported officially, you can do it on your own risk. And please don't do it immediately on the production server, test it first on independent installation.