The analogy with bike riding is both true and not true.
As someone who took his license when I was very young and then couldn't afford to fly for 15 years, I can tell you that some things don't go away, like the basic ability to fly. What does go away is procedure. Stalls and unusual flying, radio work, regulations - that sort of stuff. I could still land a 152 on the first try as good/bad as I did when I was 20 and had a newly minted PPL A.
Incidentally, I quite recently went up for 2 hrs in helicopter for the first time since 1995 and I could still hover albeit perhaps not as smoothly as at the height of my training. Point is, the physical act of coordinated muscle movement in order to fly is non-perishable, but the rest might be.
This, I think, holds true for all flying, no matter what type.