It will return to its base any time it needs to be emptied, and then resume where it was (if it need to recharge it will,generally it just continues). Depending on dust/pet hair I found this to be 45m to an hour. I ran it immediatly after it had just run (let it recharge) and it never emptied itself the second pass. I found it can run for 2h, if there is enough work for it to do and what it finds along the way (if it "finishes" and has not collected much dust it will deem itself finished. You need to look at it being a smart vac.