That's something I dont think gets discussed much here. Asphalt mat tends to dry out and get hard, which said above is counter productive to its intended application. Heck I remember buying some dynamat (original) that was already drying out on the edges just from sitting on the shelf. I didn't know any better back then, I just figured a little extra heat to soften it back up and good as new. Oh yeah... over heating the asphalt mat while applying it hurts its lifespan as well. No heat required (or wanted) when applying butyl mat, so no step to possibly screw up and damage the product.