I believe it's fair to say that with Dowty air loss, "they all do that sir".
The important consideration is how long do they take to deflate, and at what point does the regular re-inflating become an issue?
I check and give mine a couple of pump strokes maybe two/three times over the riding season, so nowhere near the overhaul stage just yet. As the forks have a Schrader valve (just the one, none of that two-bob Japanese balancing the air fork nonsense!) one of those small push-bike hand pumps is easily carried, just in case.