Leave it off with wheels chocked. The danger is that the drums rust and the shoes stick on. Also if the van goes backwards with the brake on it ratchets up tighter and remains under tension.
Trev,
As they others have already said....definitely off....I know from experience and don't mind sharing it for any new starters that may be reading.
From day one I have always let the hand brake off once the van steadies and chocks were in place.
A few years ago we drove to CC North Ledaig for a week and travelled through some very wet weather.
In my rush to get set up I forgot to release the brake and never noticed all week that it was on.
The night before leaving we got prepared for an early start, hitching the van and had everything in place for a quick and quiet getaway after an early cuppa.
Alas, as I pulled gently away, the car stalled and it felt as if i'd left the hand brake on.
I jumped out to check and realised the lever was in the release position.
Attempt 2, a few more revs and the van still would not move.
Full check around the van and car to see what was obstructing the wheels showed nothing obvious.
Attempt 3, loads of revs and the Terrano started dragging all 4 locked up caravan wheels through the gravel of the hardstanding.
It was at this point that I realised what had happened and it took over half an hour of shunting backwards and forwards and hammering of the wheel hubs before the brakes eventually released.
So much for an early and quiet getaway, but a lesson I'll never repeat,
Ken.