I know Random encounters repeat, but what if you kill, say the necromages or theif or Group of bandits in that encounter. Will this encounter not occur again then?

I noticed that for every encounter i done in a certain respawn locations, that encounter does not seem to happen again if i killed the npcs involved, at least not in that specific locations. Anyone knows how this Works?

They should respawn, with either the same encounter or a new one if you remain out of the zone long enough. There are some scripted, first-time encounters that never repeat. The hunters with a wolf captured in a cage east of Fort Greenwall, for example.

Most repeat eventually, some do not.

Thanks for the replies. I was doing quite a bit of early "encounter farming", and was sort of afraid i was using up all encounters for the rest of the game.

Yup, they repeat. Like those guys who are always drinking mead and offer you one. I usually kill them just cause, but they always come back...and still offer me some mead for reasons unknown.