I want to say something "I can work 2 hours [?] without having to reboot", and want to emphasise the two hours are not a total of several occasions I worked. My initial thought was "2 hours in a row", but I'm not convinced. What about :
2 hours in one sitting
2 consecutive hours (sounds a little heavy and formal)
2 hours at once
2 full hours
Which one are correct and why ?