How long does a debt remain with the aircraft / changing the registration?

Let’s say you land somewhere and fly on, without paying.

This is easily done at many places. At many others it is necessary e.g. Bergerac LFBE where the office is simply shut at weekends! And many airports, especially French ones (e.g. Dinard) don’t send out the bills for about 1 year.

Then you sell the plane…

Depending on who the previous owner was (for example one of a dubious reputation) isn’t a change of reg advisable?

I think, in UK law, a debt is enforceable for six years. OTOH a civil debt is not the same as a lien which is what we are talking about in the case of an aircraft.

A google on e.g.

lien on an aircraft

digs a huge amount of stuff, and it suggests liens may be more common than we think, although rather more often done by maintenance companies