The Great Suspender is a Chrome extension for heavy-duty Chrome users who keep a lot of tabs open. It suspends tabs after a certain period of idle time. This time can be configured.
You can also whitelist websites so that their tabs won’t be suspended automatically buy the extension. You also get a suspender icon to manually suspend any tab.
Here is bit of official description:
“Suspended tabs are retained after closing and reopening browser, preventing many tabs from all reloading after a restart (similar to BarTab functionality). Compatible with Session Buddy so suspended tabs are restorable. “