I tend to be a buy and hold kind of guy. My last F-250 had 13 years and 175k miles on it. My current 150 is an '07 with 113K, and I've put some money into in the last year over and above general maintenance. I don't really start getting antsy until the body work starts to rust out. Then I don't see the point anymore. Mechanical stuff? Meh...I can do most of it and the rest still hasn't covered the cost of the extended warranty, so I figure I'm ahead by now. Once the wife's Exlporer is paid off in three years I'll probably get itchy again. In the mean time, my daughter is heading to college and my son drives next year, so my desires will have to wait a while. A good maintenance program does pay off, but they can be hard on the wallet. Once the confidence factor starts hitting home, I'm looking to upgrade.
What really hurts is when you have to put money into a vehicle because you haven't decided which one you're buying. You'll never get it back out when you sell or trade in but you have to keep driving it. I had to put $1200 into my former truck to keep it on the road, then traded it about two months after. Ouch!