I don't know about you but some of my missions crashes while running every time, at the same place. This problem can be solved by hiding actor/car/objects.

The problem, I think, is when you have way too many actor/car/objects on the map at the same time. Under 20 each seem to be alright, however once you go over 20 actor/car/objects, (especially actor) the game could crash.

If you hide all your actor/car/objects after the point when you no longer need them, the game will have less chance of crashing when playing a mission and give you a much better experience. Yes it is a lot of work hiding everything after adding everything, but it really does help, so DO IT!