This post is generally aimed at the people who have many trucks or smaller outfits that have been doing this for a while. I have a 97 GMC 1500, V-6, 44k miles. It's in good shape, and I don't need to trade it in. It will be paid for this season and I have some questions. I'm wondering if it would be a good idea to keep the old truck for a while, or get a new truck for the tax write-off. How long should a truck be useful? Any helpful hints are appreciated.