How long to reheat twiced baked potatoes?

I agree with Kristine- check after half an hour - you want mildly hot, not blazing hot. And yes, cover to prevent drying, uncover for 10-15 minutes to crisp. Put a dab of butter on top before serving.

We generally advise reheating at a gentle 200 degrees in the oven for food that's already fully cooked -- it should take about 30-45 minutes, depending on how stuffed they are. You may want to cover to keep them from drying out, then uncover for the last 15 minutes if you want the top to be crisp.

In a 200 degree oven, 20 to 30 minutes.