Where are you located? What kinds of thorns? I'll occasionally get a blackberry thorn, but I try to avoid riding over them.

I was asking about goatheads a while ago.
http://www.bikeforums.net/bicycle-me...goatheads.html

There are two types of flat-free tires. Belted (Kevlar) such as on the Gator Hardshells, and others. And, adding a thick absorption layer. I don't think the layer is particularly puncture resistant, at least not on the Schwalbe Marathon Plus tires, but in theory, the layer is thicker than many of the thorns.

I've used some of the cheaper tire liners, but suggested in that thread was also the Panaracer “Flataway” tire liners which I've picked up a couple to try out. We'll see how it goes. For the most part I've been doing fine around here. My earlier concern was my nephew in goathead country. However, I recently picked up a trike, and the right tire seems to roll where it can pick up some nasty stuff.

The green goo is more or less an install and forget about it stuff, but isn't the greatest for permanent sealing of holes. Newer latex sealants are supposed to be better, but may need to be periodically refreshed.