If you tend to open too many tabs, closing them when no longer needed could be a tedious task. Fortunately you don't have to do it yourself. Dustman is an extension that closes tabs you don't need anymore. By default it closes tabs which haven't been used in the last 20 minutes, leaving at least 5 tabs open. It ignores pinned tabs and these which haven't been seen yet. If somehow Dustman closes tab which you still need, you can simply restore it using Dustman's panel.