Remember the life is not just on hours, it is also on calendar,
As an example here is the Lycoming current engine life recommendations, some engines such as the 0-360 if used frequently as laid down get a greater number of hours over their normal TBO, see
https://www.lycoming.com/sites/defau...20Schedule.pdf
The Uk then allows a variation to these hours and calendar as mentioned ( an extension of 20%) depending on certain criteria being met CAP 747 GR 24 refers, see page 346
private as said are on condition.
https://publicapps.caa.co.uk/docs/33...21JUL17_BM.pdf