Neil, I completely concur with your comments about the Supremes. I swapped from a pair of Conti Travel CONTACTs in 35C to Supremes on my Trek 520, and they just seem to ROLL and TURN much better! I chalk it up to the tyre profile, sidewall construction and tread-sidewall transition. The Contis had a horribly square profile and unforgiving sidewall, but I also didn't know what I was missing until I switched.
On the subject of repeated punctures, in my own ham-handed experience, the skill of the practitioner has an enormous bearing on the longevity of the tyre/tube combination. I know it should go without saying, but it is absolutely essential to install the tube correctly (neat and even distribution around the rim, no pinch points, perfectly clean rim bed, high quality tube and rim tape, etc.). I have recently tried lightly dusting the tube with talcum powder before installing it in the tyre, as an aid in tube alignment during inflation. No flats yet!
I dunno what happened on my recent rail trail ride. My Victorian hosts all sagely agreed I must have collected a "bindi", but I could find no indication of it despite forensic examination of the tyre. On the other hand, I did find some sand grit, which may have entered during water crossings (?), or when it was being ridden while flat. I'll never know...
PS - The same wheel popped a spoke yesterday! Lightly loaded, at speed on some sharp bumps. It's hurt my pride as a wheel builder (first time), and brought me down to earth (not literally), but a good lesson nonetheless.