We leave ours inflated on a launching trolley all season. It gets a good hose down after a weekend/weeks use on the trolley with tubes and keel inflated to get as much sand out as we can. Let water drain out of bung with bows elevated although always remains wet under the floor. Gets a good clean and dried before deflating and stored in warm garage over winter.
Not noticed any loss in pressure but always leave tubes at half pressure (0.15 bar) and keel deflated when not in use/stored and boat covered.
Pressure readings will vary dependant on ambient temperature though.