I fell asleep/slept for

These are correct:

Last night I slept for five hours.

I fell asleep before you came (home) last night.

In fact there's nothing wrong with the grammar in the second sentence. It does sound a bit odd, though. I think part of the reason is that people normally want to sleep at night, but there's usually something involuntary about falling asleep. On the other hand, one could easily fall asleep for a moment or a few minutes -- so maybe 5 hours just seems too long in this case. Anyway, all I'm saying is

ozzourtiall I'm saying is that the sentence doesn't really break any grammar rules.

Technically, no, it doesn't. I'd say it's in the category of semantic contradiction, like

Jack won the race for 5 hours.

where the verb suggests something instantaneous, and the adverbial doesn't apply to instantaneous actions.

CJ

Jack won the race for 5 hours. sounds decidedly odd.

Jack fell asleep for 5 hours. seems better to me for some reason, even if 'falling asleep' is an instantaneous action.

Here are just ten similar examples I found on the Internet:

After returning to the

ozzourtiWould you replace "fell asleep" with "slept" in all of them?

No — except maybe the first one. I don't want to put words in other people's mouths!

Thanks for gathering all that data. It's quite revealing. Apparently, to many people, "fall asleep" can be used to mean "fall asleep and stay asleep". They do all strike me as strange, though.