If your on site for a few weeks on the jacks you may find that your handbrake sticks on when you go to move on, this has happened to me a couple of times, so now if I'm likely to be parked up for longer than a week i leave the handbrake off when i've levelled the van, i have so far always remembered to put the handbrake on before lowering the van but I may leave a note on the speedo to remind me in the futureI can see no reason why you would have your handbrake off when you are up on your jacks in the first place.
