The 12 year inspection has always been there (or all the engineers are wrong) (unlikely).
Its just that the rash of 44s that were bought in the late 1990s are reaching that age so you are seeing this as an option now whereas before most were at schools and got closer to 2200hrs at 12years so had the rebuild.
The engineers view was that at about 1400hrs TT at 12 yrs its worth the rebuild than the inspection. I'm not sure where the 1000hrs line came from as I can't find it written anywhere.
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