Are gliding and wheel walking (+other more advanced skills) skills that are “retained”? For instance, I didn’t touch a unicycle for 20 years and when I picked it up my first ride I was able to idle and ride backwards (a little rustily). Would the same be true of the more advanced skills? 
I would imagine to some extent they are. For example, I didnt try wheel walking for almost a year when I broke my foot, yet I could still do it fine. Stand up wheel walk was the same way, but a bit shakey. I would imagine however, that if it had been 5 or ten years as opposed to one, I would have had a significant difficulty.