I'll throw my 2 cents at this - Whenever a tractor is shut off everything should be lowered to the ground so if the valve levers move nothing else does. On a backhoe, the transport lock can be used - but resting it on earth is safe and easy.
On the leak-down issue, they all do it - some more than others. Pilot-operated check valves help, but piston seals can still allow some creep.