Potentially the recordings and timers could all be renumbered to start consecutively at zero on some regular schedule (e.g., daily), or via
Renumbering would defeat the purpose of keeping the numbers constant ;-)
With just 8 digits for the ID, you could do 1000 recordings a day and still not overflow the number space in over 270 years. Or more realistically: over a lifespan of 10 years, a VDR instance would reach five-digit numbers only with at least three recordings daily, and six digits with 27 recordings daily.
Olaf