I service cars and light trucks professionally. ANY vehicle can be made to last "indefinitely" if it is cared for properly, not crashed beyond a reasonable ability to be repaired, or rot away into its basic elements. It is a myth to think the numbers in the odometer have anything to do with some made up finite number of usable service life. The car I drive every day, 100 miles a day, has currently 536k miles and is 18 years old. I'd hop in it today and drive it across the country worry free. Because it is in good order, because it is a good car and I keep it that way.
Some will require more TLC than others, and some will be less forgiving for neglect than others.
As far as Sprinters, we regularly see some in here with over 250k miles that not only still run and drive good, but still look good too. And even a few with over 500k miles. And many of these are fleet vehicles that get treated pretty rough or at least not "babied". The ones that are owned by private individuals are often nicer (cleaner) and will obviously be in nicer condition as time goes on.
Some tips for keeping something in good order, especially if you buy it new:
Clearcoat everything underneath that you can get to. All the nuts, bolts, brackets, axles, control arms, everything... clearcoat it. Do it when it is BRAND NEW, and it will keep everything looking nicer for longer, and will help down the road if something needs to be serviced.
Undercoat areas that may need some extra protection, especially areas you cannot easily see. In some cases, this means taking wheels off and removing plastic fender liners, etc. I use Flex Seal, as it actually works better than even the nicer canned undercoats like Wurth. Do not plug up any drain holes, but get it everywhere you can. It is also a great sound deadener. Drop the spare tire down and do up above that too. Clearcoat the insides of the wheels while you have them off, then once dry shoot some spray wax on them. It keeps mud, dirt, salt, ice, debris from sticking too them too. No out of balance wheels caused by a chunk of ice stuck on the wheels if it cannot stick!
Wax all the painted surfaces. Everywhere. Inside and out, anywhere you can. Door jams, seat pedestals, kick panels, everywhere. Don't forget the roof. Pain I know, but do it now while you can, it will make washing much easier and stuff won't be as likely to stick to it.
WD40 periodically, especially in winter. Stuff works great, keeps things protected, won't hurt anything. Just keep it away from the brake friction surfaces.
Maintain it by the book, and then some. Keep fluids topped up and changed when necessary. Don't neglect the brake fluid.
Use the parking brake, BEFORE you put the transmission in Park. Let the weight of the vehicle rest on the brake, not on the park pawl. And keep the parking brake mechanism underneath lubed. You'd be amazed how nice and tight the gear selector linkage is even half a million miles later when it has never been used to yank a tiny chunk of metal out from underneath the weight of a giant van resting on it.
Look things over periodically. Overlooked items like one-way alternator clutch pulleys or seeping power steering reservoirs can eventually cause a much bigger problem if neglected.
Be an advocate for your vehicle, and it will last a good long time. While my Sprinter is only a baby at two years old, I can show you my 1991 Jetta and 1996 F150 that darn near look as good as they did when they were new. Care works, and will cost you less money in the long run.
