I watch all 3 of the fishing shows: Deadliest Catch, Swords - Life on the Line, and Lobstermen. (I didnt even know the last two existed until the Tivo recommended them) Two of the shows are traps on the bottom, and one show is a longliner for swordfish.
It seems they all beat the snot out of their boats, especially the swordfishers and the lobstermen since they're relatively small (65-85ish feet).
I havent seen an aluminum boat yet on any of the shows (there is one smallish fiberglass boat, and he get the snot beat out of him regularly) and all of the steel boats show a lot of corrosion and repaired damage.
So, how long does a commercial boat last?