While we do not do any loaded touring any more we have had great luck/usage out of Maxxis Re-Fuse 700x25 folding tires on our tandem. Running 120 PSI.
Put 5,600 miles on Re-Fuses (get about 2,000+ miles out of rear tire, a bit more on front) in 2011 and had one flat.
Not a puncture, but old patch that came loose!
Currently trying out Panaracer Pasella folding 700x25 and so far no punctures in 1,794 miles. The Pasela is recommended 115 PSI but rides a bit harsh for stoker, so we run it at 110 PSI. So far so good!
Just our input.
Rudy and Kay/zonatandewm
We do live in the Sonoran Desert and along with chipsealed road/ usualroad debris we get a fair amount of catus needles.
We are a rather light team (+/-250lbs)