How long do you keep your truck?

First pickup in 1987 and kept it until 1993 when I realized the old 350 3/4 ton with a 4.10 rear end was not enough truck to pull both my fifth wheel and boat all the time. Last trip with it I got 5.3 mpg and almost didn't make it to the next town to fill up. Got a 3/4 ton 454 in 1993 with a manual transmission and had it 20,000 miles when we traded out for a new Vortec 454. Got rid of the 1993 because it had a problem with its sensors, it would simply start the speedometer toward the top speed, peg out and then go into limp mode. Dealer/friend tried everything to figure out the problem to no avail. He traded me out of it for $2,000 for the 20,000 miles I had on it and I got the Vortec 454. Really liked it a lot, but decided I "needed" diesel so got a new one in 2002 and used it for 103,000 miles and replaced the PRNDL switch four times, the last time the wife said that was enough, well she said I could get a new truck. So, in 2011, got a Dodge diesel, long-bed crew cab with a six-speed manual and a 3.42 rear end. As I was getting old, it got harder and more difficult to back the truck with both feet on the pedals and turning around to watch my backing, I know, I should use the mirrors. Also, hated the mileage and when I added to boat to the load, I was uncomfortable with the perceived lack of towing ability so, June 2012 bought bought another GMC D/A short-bed crew cab and have a little over 20,000 miles on it. Love the power, get decent mileage and figure this will probably be my last truck, absent mechanical problems, as I am now over 70 years old and don't have enough towing years in me to wear out this truck.

As you can see, I don't keep the trucks a long time but, in my mind, I had good reasons for getting rid of each one of them.