CleanTabs от Pen

Auto discard (sleep) / close tabs based on rules.

With CleanTabs, you can
1. Discard (sleep) google search after leaving 10 minutes.
2. Close stackoverflow after leaving 30 minutes.
3. Don't worry, closed tabs will be stored in stash, so you can still visit it later.

Source code: https://github.com/heyppen/CleanTabs