The vertex are not made by PC, they are used std on some huskys and ktms, they often last a season in those bikes but i wouldnt go that far on a 125, i have a vertex in my Cr and replace it every 12hours at expert level.A novice should easily go 25hours between changes.PRO X are
made by the same manufacturer that provides the jap bikes so effectively you are saying std good but std is bad.If you are getting 3 rides on a piston i would look at
1,jetting-are you way too lean?
2 Airleak-again cuasing it to run lean.
3 dirt causing fast wear on piston.
4 ports not champhered properly causing ring wear
5 cylinder out of round or worn beyond spec.
6 too much compression causing detonation.
7 too little oil in you mix i use 32:1 on a 125.
Hope this helps.