I shut mine down during every water change...I can do them pretty quick. If I am going to have them off for an extended amount of time I will stick the media in a bucket of tank water.
I find that hob always have enough water in the impeller cavity after suction loss, so lubrication isn't loss.I have always turned off my filters when doing water changes.I thought leaving the filters running with no water in them would burn out the motor or the impeller.
I also clean out my filters with every water change....well I try to anyway.I don't worry about bacteria loss as I suspect that there is enough of a population on the various surfaces inside of the tank that does not die off.
Intetesting,I saw that in an earlier post.I'll keep it in mind.I find that hob always have enough water in the impeller cavity after suction loss, so lubrication isn't loss.