Word choice of "much" vs "many", like "too many hours", but "too much time" [duplicate]
Solution 1:
Wow! this is a damn good question. In my opinion, when you associate the number of hours, it becomes a countable noun for that reason using "How many hours" is valid for time context.
The other example I can think of is that "How much milk?" vs. "How many cups of milk?" Here "coups of milk" is a countable entity, and for that reason, we can use "many." I hope it helps.