I'm like nashcommguy in that i get a little bit fanatical about not getting flats for reasons of convenience and money-saving. I've never had a Marathon Plus tire or an airless tire, but I tried using more than one tire liner inside a kevlar-belted bontrager tire, and the stupid bits of wire/glass one picks up in Philadelphia still would poke through. I noticed, however, that the types of 26" tires with lots of rubber, that provide at least 5mm of distance between the tube and the road surface.... never get flats from these common bits of glass and wire we have here that are less than 4mm long. (who would have guessed!) I have become convinced that a way to avoid flats where I live is to avoid tires that allow the tube to come within 5mm of the road surface. I'm thinking about inserting one of the lightweight pieces of foam pipe-insulation you can buy at Home Despot as a buffer between my tube and the road. (This will do nothing against nails, but I had 1 or 2 nails drive themselves through my kevlar belted tire when I was using it, anyway)