your choice--
i have flown with airlines that had us turn it on when doing cat 3A approaches--
also, on the 3/400's it often took two starts to get the thing going.
the beauty is--at least in the left seat--you can leave on if you wish and turn it off when you wish. weigh the options and make your own decision.
the fact that some APU's have gone bad, should be measured the same way--how many times in a career would that happen.
i've never left it on up to 10,000 ft---intentionally that is! ha.