Dan Luke wrote:

Is calendar TBO something that is generally ignored?

From what I can see, it's pretty much ignored. Most owners of older aircraft to
whom I've spoken about it seemed to be unaware that there is such a thing. When
informed, the usual attitude is "Well, I'm not going to worry about it." IIRC,
it's 15 years for the Lycoming O-320 series.

Should a prospective buyer make a hard negotiating point about it?

In the current "buyer's market", you should make a negotiating point out of
anything you can. I doubt that you'll get very far with this one, though. Even
the mechanics I've spoken to about this say the time TBO isn't important.

George Patterson
Some people think they hear a call to the priesthood when what they really
hear is a tiny voice whispering "It's indoor work with no heavy lifting".