I've never used an ST46 but back in the day I had an Enya 45 model 6001 (the first version with twin rings) and I recall our then current Aussie champion (Peter White) asking me how I got it to run just like his ST46. I had no answer for that because it was bog standard and ran it with straight 75/25 all castor fuel. However after ~2000 flights, which equates to ~200 hours of running, it was starting to take as much as 5 or 6 flicks to start (instead of the usual 1 flick) but once running it was as good as ever. Regardless, I fitted new rings and it was then back to its 1 flick start again.
Much later I went to an ST G51 and it was simply brilliant. Bog standard of course and has never shown any signs of wear. My next ringed stunt engine was the Enya 61CXLRS (the one with a head button, not the later red head ABC) but once again shows no signs of wear.