A workspace that nobody is using does not stay running forever. After a quiet spell it goes to sleep. Its files and installed tools are saved, and it wakes when you or the assistant need it again.
A workspace sleeps after it has been idle for a short while, meaning no task is running in it and no one is using its terminal. A workspace never goes to sleep in the middle of a command, so a long task is not cut off. The exact length of the quiet spell is set by StellarFirm and may change, so these docs do not promise a number.
The state badge changes from Asleep to Setting up and then to Ready. Waking a saved workspace is much quicker than the first start, because the tools are already installed. The view refreshes by itself, so you do not need to reload.
If a wake does not finish, the badge says Setup stopped. Press Try setup again. Your files are still there.