Here's what I do all the time.

If I'm making dinner, and then going to pick up the wife (about a 90 minute round trip most days), I'll put the dinner in the oven and cook it for a while. Just before leaving crank it up to 450, and then turn the oven off. By the time we get home it's cooked through, and the oven is still more than warm enough (our oven holds the heat for hours). If it's not done, just crank the oven back up and finish it off.

That works best for things that cook for a while and are forgiving in the cooking time (like beef shanks or short ribs, where it really doesn't matter if it's seven or eight hours at 250), of course it would not work for something with a 20 minute cook time.

I don't like leaving the oven on, that's just me. I've never had a problem with the oven, but should something happen, it's probably better somebody is home. Millions of people use the auto on or auto off or the sabbath mode when they are not home, so there's probably no real concern if you choose to do so, but if you are delayed for some reason because of traffic or flight delays, whatever, your food will just keep on cooking and cooking.