STL vehicles are usually used for 8-10 years (at least two missionary 4-year terms) and then sold…with the sale funds then applied to other STL projects.
However, sometimes a missionary is able to use his/her STL vehicle for much longer. In one recent case, the Madagascar Field used a 1996 Kia 3 ½ ton truck extensively throughout the island in building churches, doing work and construction projects, etc. It was recently traded in on a newer vehicle…but not before it passed 1.1 million kilometers on it!
Surely God loves and blesses these vehicles and sustains them (and our missionaries!) throughout their many years of service.