Till the wheels fall off.
96 Tahoe has 272,000 miles, and too many repairs to be a beater for the wife during bad weather.
Prior to that I had a 90 Mustang 5.0 fast back. Went 126,000 and traded in for the Tahoe. Eninge was leaking fluid into oil and would have crapped out so get rid of it before it does. Too many services for all kinds of bugs. But it was fun and does a good vroom vroom.
Prior to the Mustang, '80 Volvo 245 DL wagon. Bought it used at 160,000 after I wrecked the VW. Put another 30k on it but it too had too many things to replace. I was literally buying a new car part by part and would conk out with another worn out part leaving me stranded time and again. Traded it in for the Mustang.
84 VW Scirocco. Was stationed in Hell Hole, New Mexico, in the army and put over 45,000 a year on it. That was just going to town for mcDonalds, going to town for a movie, or just getting to town to keep sane. Close to 98k miles when someone cut me off and caused me to roll it twice on the freeway in 1987.
83 VW Golf. Put 38,000 miles on it and had to get a faster VW--the Scirocco.
With the price of cars, it only makes sense to keep it for at least 7-8 years to get your money's worth. That new car smell is great but buying a new car eveyr 3-4 years means you are perpetually making car payments and not getting the car's value over the long run. I would have stayed with the Tahoe but for the constant repairs when it has so many miles on it.
Hope the 4Runner gives 250,000+ miles.