Reaheating 2 Spiral hams at same time
If your oven can maintain the set temperature, and there's adequate spacing between the two hams, you shouldn't change the time.

Note that I'm assuming that they're both going next to each other on the same rack of the oven -- if this were casseroles, you'd have to increase the time slightly and swap the two part way through, as they'd end up shielding each other from the elements.