When you use the perfective aspect of the verb, does it matter if, say, the action happened several times as long as it is completed or does it have to be just once? In that case do you use the perfective or what?
Here are some examples of what I mean:
Он убил/убивал многих людей в марте.
Это произошло/произходил много раз (вчера).
В течение недели он увидел/видел четырех людей.
Он вчера просмотрел/смотрел два фильма (not at same time, ie with a 5 hour break in between)
Hmm, I hope you know what I'm on about because I don't.
Thanks a lot.