AUF initially messed up on rego numbers, not forward thinking enough to imagine more than 999 planes, computers, databases and further categories. They had to rescind some numbers (one of our planes was a victim) to sort it out. In an ideal world a unique number would follow the plane from cradle to grave and not be reallocated. Remeber the scandal of 001 that was taken by a former President of the AUF for his plane, when the original 001 plane was being rebuilt?
I think the numbers are starting to run out. Ultralights, particularly the early home built were retired due to technological obsolescence, unobtainable parts, engines, structural integrity, aging owners and an inability to find any buyers. That happened to our Wheeler Scout. Numbers were allocated to builders, who then never got the plane registered. So it does make sense to re-allocate numbers for planes that will never fly again. However, there are people who rebuild and want to keep the rego, even only to save the history and the work required to change placards and decals.
I agree, it is nothing new, my C152 used to be a DC-3.
An issue I see, is that the last owner on the RAAus books may not be aware of who owns it now. As it costs money to keep a plane on the RAAus register, owners are more likely to let it lapse until they can get it airworthy again. They can sell and not inform RAAus. On the other hand, VH regos are free and perpetual, provided you don't inform them that it has been scrapped.
Because I have so much history of AUF aircraft, I get enquiries from people who have found a plane and want to do it up. While that may sound like the future is bright; most of these will never fly again. My first port of call is the RAAus register, which gives me basic detail and when it was last registered. I can then have a look at the accident database (prior to that date). Then I look at the history I have. At present we are looking at 3 planes returning to the register once the ACR is done, and others in the process.
AUF solved their 999 plane problem by putting a 0 in front making the range to 9,999. Perhaps RAAus could put another 0 in front? I just want them to keep the history visable.