I see. But it needs to be considered, that the inner circles are written onto more frequently.
UDF sparse/sparing tables can keep track and balance the outer/inner edge writing cycles, but once the disc is reformatted, the sparsing tables, which is a part of UDF itself, is lost, as far as I know.
Another approximate way is verifying the burning quality. It should not decrease much for the first 900 cycles, but then, it should plunge.