Finally took my '07 MCS in to the tire place to have my slow leak checked out. Front tires have been holding air well, the rear tires, not so good. Before, it seemed random which tire would lose pressure, but now it was reliably 1 week to the tire monitor alert, left rear would be around 28PSI, right rear around 35, down from 40.

They said there were nails in both, and it was fortunate I had Dunlops rather than Pirellis, as Pirelli won't let them repair runflats.

I'm now plugged and rolling more confidently. Still I'll carry the compressor around for a while.

I also remembered to remove my MINI-branded valve stem caps before taking it in, as I know from experience they consider whatever's on there to be trashable.