Google Chrome uses too much memory if too many tabs are open, reason for this is: it opens separate process for each tab to prevent crashes of Chrome. Tab Wrangler is a Chrome extension that automatically closes unused tabs after 7 minutes by default and allows you to re-open them from Tab Corral tab in extension Options Window .
Auto-Close Unused tabs and access them whenever you want with Tab Wrangler Chrome extension
This extension allows to lock the tabs from auto-closing. You can choose these tabs from Tab Lock tab.
You can always re-open the auto-closed tabs by this extension from “Tab Corral” tab by clicking on tab title. You can also add URLs in the options to auto-lock those tabs, those matched URLs will be automatically locked.