Why would you want to do that? Burning up one car while keeping the truck low miles (and running forever) sounds like a pretty good strategy. Miles are miles. If you are going to travel the same number of miles, why would it matter if you spread it over 2 vehicles? You can keep that truck for another 10 yrs and replace the wife's car as needed. 70k in 3 yrs means 210k in 9 yrs. Right about time to let it go, I'd think, both age and miles.
Except I have heard that non-usage is almost as bad on a vehicle as usage.. My truck is not the most comfortable thing but its OK for longer trips and my wife HATES to drive it due to its size..
I am also thinking that resale/trade in on my truck at a good time.. Also I have ppl talk about their dodge vehicles having paint issues and electronic issues as they got older and my truck is in great shape right now..
And the biggest reason is - I can afford a new car and like the idea of something smaller that fits our overall needs better..
Brian