Hi, Roro:
Thank you four your insightful comments on the question.
On a note slightly related to what you've suggested, I should have pointed out first and foremost that the point the questioner seemed to be stressing about it all was that the omission of the preposition "for" in front of words describing time or distance is often permissible in terms of grammar in sentences like:
"I've lived here for ten months," or "I've lived here ten months;"
and
"I ran for five miles this morning," or "I ran five miles this morning."
I have no idea which souds more natural in either case, though.