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 ?
As an American speaker, I would use the phrase “two hours straight” for this meaning.
“Two full hours” or “two whole hours” would work too, but they are just a little bit more ambiguous.
“Consecutive” would work, but it sounds too formal. I think “in one sitting” usually refers to what you are doing, so like, “I ate two pies in one sitting” not “I ate pies for two hours in one sitting”.
And as mentioned in the comments, “two hours at once” is pretty much impossible.