OK, let's put things in perspective.
Are any measurements being taken or are we just throwing parts at engine with no true idea whether they are true needed or not?
The manufacturers and the A/M parts industry sure has all you folks scared silly. Many, many, seriously....MANY parts are being replaced long before their time.
A true mechanic/technician will measure everything. Especially the NEW parts. How the heck to you expect to know if something is worn if you don't know it's original measurements???
You can't just say a piston is done in 20 hrs. First off, unless you're JS/RC/ or dare I begrudgingly say Chad (the king of whine) Reed, you will very unlikely be able to kill any engine part in 20 hrs if properly lubricated.
Especially a 2 stroke piston! Give me a break! If you have it jetted correctly you could not possibly wreck it that fast. The bikes these days are built too good for that.
Don't believe me? Well then, take the motor apart and do some measurements. The tools won't lie to a person that knows how to read them.