I didn't like the weight of the Schwalbe Marathon Plus, so I went with the Continental Travel Contact on my LHT. Had one puncture in the 2,600 miles since I put them on.
http://www.conti-online.com/generato...ontact_en.html
You might also consider Maxxis Overdrive, a Kevlar belted tire. My wife has 5000 miles on her current set and has yet to have a puncture.
http://www.maxxis.com/Bicycle/Hybrid/Overdrive.aspx