Had it done over the winter. No issues at all thus far. The 144 piston weighs about 1/2 an ounce more than the stock 125 piston, so there's very little extra weight to put stress on the bottom end.
I haven't replaced either the ring or the piston yet. Iwas going to ring it last week, but everything checked out ok, so . . . The motor has approximately 15 race motos, 6-8 practices and 10-15 other hours of play riding/practice on it.
Dirtrider.net member "bclapham" also had a 2002 RM144. If I recall, he was 200+ lbs and racing at very hilly Glen Helen. If I recall, he replaced the ring every 5 races and the piston every 10. He replaced the crank at one and one half seasons.
Eric Gorr recommends 5 hours for rings and 10 hours for pistons for non-expert riders. (Note: That's actual ride time - in a typical 2 or 3 hour "ride" I find I'm actually on the bike for maybe an hour.) Eric's recommendations are just that - recommendations. He's seen an expert blow a 144 motor in an hour, and he had a 144 go 100 hours on the same piston.
It's all in how you ride it. Use a good 2 stroke oil (Eric recommended Mobil1 Racing 2T) and you should be good to go for quite awhile.