Muz, if you read my post, MMF doesn't save identical objects more than once. If you copy and paste the player object in to a new frame MMF isn't going to save it all over again, it's cleverer than that.
I never had to use THAT much frames! When they start to get ''full'(if thats even possible) then just make another game and find a way to connect both to eachother
If you want to keep the filesize down (if only a little) you could make a larger area in one frame and put more than one area inside it.
say for instance in a village, you could make the houses in a different area not accessable normally but in the bottom left and your character warps there when they open the right door. Maybe lock the scrolling too to make it look like a seperate area.
I feel that is better than making a new frame for each room.
Each new blank frame adds 5.4k to your filesize (The Games Factory anyway maybe MMF is more?)with over 160 frames this adds up. Well it's not much really.