Dicky Ticker

IMO-Not retest after all the test is only proving you can operate the machinery and drive to a minimum standard,with no medical from a doctor
21-50 every ten years,50-65 every 5 years 65-70 every 2 ears and 70 on wards annually.COMPUTER SIMULATED ASSESSMENT + MEDICAL,even if only an eye examination, and if you fail either after a second attempt having had treatment for medical or addition driving training,prohibition till you have taken a statutory more complex retest and strict medical..Harsh but being honest would eliminate a lot of the people who drive with medical conditions that interfere with good driving,as well as the incompetent.
My personal circumstances dictate that I must have medicals to keep my license and I appreciate that if I don't reach that medical standard I don't deserve to have the entitlement to drive.I would be willing to do assessments as likewise I would want to know that I was considered proficient enough to satisfy the required driving skills,not just my own judgment but satifying the required standards by the assessors.

P.S. I would add that this would be for the highest classification held on your license and not for every type--example being if you have a car license this would also cover you for your bike.
Your driving license is based on attaing certain levels that entitle you to drive and at the moment you have nothing after you have passed your test apart from self declaration on the medical