My little 1974 Grumman AA1B has 2440 hrs total time on the original engine (Lycoming O-235 C1C). All 4 cylinders were replaced with new at 1800 hrs and I fully expect the engine will last longer than my flying career.
It flies 50 to 60 hrs airtime a year, but it never sits more than 2 weeks between flights and the oil is replaced at 25 hrs or 6 Months, which ever comes first. Regular use is the secret to engine longevity.