I would say the trackpad will hold up alot better than a trackball in terms of durability.
the fact its not a constantly moving part, affected by dust, lint, moisture etc.
It also wont be discoloured, but the scratching might be a problem. just like any other part though.
"That's it then. Cancel the kitchen scraps for lepers and orphans, no more merciful beheadings... and call off Christmas."