Set up my PTG/II less than 2 weeks ago (Heybrook TT2/LVX); you're right, break in is almost nonexistent.
Been using AT MC's for 30+ years, specifically OC9 and OC9ML.. These carts required 10-20 hours to break in, and overall sound is a bit leaner than the PTG/II and also a slightly more analytical.
Prefer the OC9's on live rock LPs but the PTG/II on just about everything else.
Despite the PTG/II being rated at .3 mV and the OC9's at .4 mV, output through my NAK CA-7A pre-amp appears to be almost identical.