Hours are as follows:
Total flying the machine = approx 100 hours
Total running the machine (i.e. tick over, warm up etc) approx 140 hours
Total flying the machine on new piston only = approx 30 hours
Total running the machine (i.e. tick over, warm up etc) on new piston only = approx 40 hours
As you can deduce, the piston was replaced at around the 100 hour total running time. I run the engine for typically 15 minutes prior to flying it and most of my flights are between 45 mins and 1hr15mins in length.
Regards
Stuart