This is not that complicated. Inspections to be performed by date (Annual) are just that and so the total airframe/engine hours are irrelevant. Each time the inspection date applies the one month extension may be used. The hours are the hours and so the 100 hour inspection is always due 100 hours from the last inspection but the +10 hours may be exploited. The 100 hour may be from the annual or the last 100 hours inspection, as applicable, because all elements of the 100 hour will also be part of the annual inspection.
There is no accumulated benefit in either case even if the extensions are always exploited. There is not a date or flight hour when an inspection must be "started" but flight is prohibited when an inspection is due (plus extensions) until the inspection is completed and signed off.
Last edited by Fl1ingfrog; 17th Oct 2021 at 11:44.