I've used the Marathon Pluses and find them way too heavy and not good on wet roads, though they didn't get any punctures on 1000+ mile tours. But, instead of puncture resistant boat anchors, I've switched to Ultra Gatorskins with tire liners. They are much lighter, grip better on wet roads (I live in SF and ride on many wet roads), and I still haven't had a flat, lately.

In 2009, I rode over 1500 miles with a UG on my front tire. I now have UGs on both tires but haven't toured with one on the back yet.

YMMV,

Ray