On my LHT, I have contact tires with 2000+ miles on them. Recently I have been getting a lot of flats. I few weeks ago, I stopped by my LBS to get some more patches and tubes. They asked me if I would test "CafeLatex" foam tire sealant. I volunteered..... they put the bike on the rack and injected the "CafeLatex" in through the presta valves then pressured the tubes/tire up.
I have yet to get a flat since the installation (about 500 miles). so far.... so good.