Max (Hello, hope things are OK with you) I'm guessing Mark has the T40 (unless he's rounding up a T38 to 4m long) which will be an alloy floor with low pressure keel like mine. Still important to get the boat up to pressure for best performance.
Really you should get a pressure gauge Mark, I like the one that's seperate to the pump as it's easier to do a check in the middle of the day without the hassle of attaching the pump. I think this one will fit a Honwave but ask the seller first if you think of buying.
INFLATABLE BOAT PRESSURE GAUGE, Europa Sport, ** NEW ** | eBay
I see a bit of a problem if you do leave the boat inflated on a hardstanding for long periods as GJOKYZ hints. If inflated at the correct pressure for use this week at 13 degC then a summer 25 degC plus day with the added reflected heat from a hard surface could risk stressing or bursting the tubes. So ideally you'd leave it a bit soft and top up on the day of use.
However if you leave the tubes soft (and assuming it's an alloy floor) it isn't ideal to have the transom held up on the wheels because the tubes will want to sag like a banana but the floor will stay rigid. The Honwave alloy floors have some fairly sharp edges and the tubes have small areas of reinforcing where the floor edges touch. But if the boat goes out of shape the floor could snag on an unprotected area.
If I have to leave my Honwave with the wheels on as you're thinking for more than a short time then I have a fat inflatable cushion I place under the keel below where the first alloy floor section is... i.e. about one third of the way back from the bow. Makes it sit level and better supported.
Are you leaving the outboard on it when stored, what outboard did you get?