Actually over the last 20+ years I have seen more "experienced" and highly certified/qualified divers who are fooled into believing that they are better than they are. I won't go into "Normalization of Deviance" and just say some people just get too relaxed and overconfident with time and experience. It may be overconfidence has eroded the skill of a diver who is still diving "regularly" and the hiatus may have nothing to do with the loss of skills. That is why the question can not be answered.Thank you for your contribution. You're right... Being that there isn't a known set of dives to complete does make it harder to know if your skill level after the hiatus will vary. I believe it will and with greater experience, veteran divers might, as well. It's the beginner that is often fooled into believing that they are better than they are. The industry is definitely vague about the entire concepts of ongoing training and refresher courses...
I wouldn't necessarily advocate for a refresher course but a skills assessment by an experienced diver who can give a reasonable assessment. That is a better way than pushing for a set number or dives in a set time frame to determine need for a course... unless you own a dive shop of course