Does flying past TBO cause insurance issues should there be an accident or incident?
Some policies have restrictions on going beyond TBO, so flying past that point would void that coverage. But AFAIK, most policies don't have any such restriction, so flying past that point would not affect that coverage. Read your policy to find out where you stand.
For most all of us part 91 fliers, time between overhaul is not mandatory to comply with. Therefore, an engine is not unairworthy just because it is, say, 100 hours past manufacturer recommended overhaul. As long as it has passed its last annual or 100-hour inspection, it is still airworthy.
Insurance companies could deny a claim for flying an unairworthy aircraft. But, as Ron noted, unless your policy specifically prohibits flight when beyond TBO, the engine remains airworthy as long as the aforementioned inspections are up-to-date.
THANKS everyone - really appreciate it