Frozen track?

because your sled is warm, it melts the snow underneath the tunnel and even the snow its sitting on, which then freezes. Effectively, when you start up in the morning the track is frozen to the ground so you'll burn a nice section out of your belt each time you do this. Make or buy a rear stand, and when you stop riding, put the rear bumper up on the stand and spin the track to rid the suspension of built up snow and clear out the tunnel. Or, before you ride, pick up the rear of the sled and hoof it up and down a few times to break it free of the ground, this will also break up any built up ice from your suspension. Lots cheaper than buying new belts