The phrase "again in three hours" is correct and usable in written English.
It can be used when indicating that something will happen or be repeated after a duration of three hours.
Example: "We will meet again in three hours to discuss the progress of the project."
Alternatives: "once more in three hours" or "reconvene in three hours".
It could equally be the case that they said it four hours ago, and will say it again in seven hours' time.
"When I was released we organised a press conference and immediately after it, Lukashenko said that if there was another word we would be in jail again in two hours," Sannikov recalls.
We got through the East Coast show and everyone was jumping and screaming in the control room and I was so happy, and then I was like "Oh my God, we have to do this again in two hours".
Mr. Schulberg and the director Elia Kazan get the Nietzschean peapicker and crackerbarrel fascist Rhodes Andy Griffithh) from the outhouse to the penthouse to the front door of the White House and back again in two hours.
The host was a terrific cook, but one of those seven-course terrific cooks, disappearing into the kitchen for a quarter of an hour at a time to execute the latest Ferran Adrià recipe, while we all secretly gripped the underside of the dinner table, realizing that the babysitter meter was running and we would have to be up again in six hours to dress the kids and get them to school.
What a relief, then, to tumble into the trencherman's world of Calvin Trillin, where eating is about satisfying appetite rather than chastening it, table rituals are kept to the minimum consistent with a modicum of civilization and a happy gluttony is the norm, with only the knowledge that you're going to eat again in two hours keeping you from eating even more right now.
Today ships can dock, unload and be out to sea again in seven hours.
This is as dark as it will get, then the sun will rise again in five hours.
