Tab sleeping or Tab snoozing feature has been around on other modern browsers for a while. Some are using extensions and some have the feature built-in. Now Microsoft Edge has joined the group with a tab sleeping feature right out of the box.
As you can see, the sleeping tab is there to save resources and to improve the performance of web browsing. And because it reduces the amount of memory used for the browser, it also improves overall system performance.
Since Microsoft Edge version 90, the tab sleeping feature is enabled by default to put inactive tabs to sleep after 2 hours of inactivity.
However, if you are not fond of the feature or just want to tweak the setting a bit, you can still do it through Settings.
Go to System pages in settings via edge://settings/system.
Under the Save resources section, you can disable the Tab Sleeping feature by sliding the switch off.
Or, change the time of inactivity to anything that works for you.
Or, add websites that you want them to be live at all time.
I would say, give Tab Sleeping a try first before turning it off. If you are the one who always leaves tons of tabs open, you may get a lot of memory back with this feature.