While cooking with gas is nice, I don't necessarily mind if the stoves are electric when living in an apartment - I get weirded out and worried about gas leaks and stuff blowing up. I wonder if your oven cooking time issues could have anything to do with the seal around the door becoming weak and leaking heat out. Do you notice your kitchen getting abnormally warmer than usual when baking something, for instance? Are the burners on your stove weaker too?
We have a combo microwave/convection oven too - but I almost never use it as an oven, it's too much of a pain in the butt. I have to remove the plastic rotating ring, then I have to find the wire rack to insert in it. But the worst part of it all, is in order to choose the temperature and set it to convection mode, I have to flip through a ton of screens on the LCD panel, which takes like 10 minutes, no jokes. And this is a KitchenAid appliance, you would think they would make them more user friendly than that. Plus, on top of it all, since the walls are so close to the food, they get covered with grease splatters if I am cooking anything oily.