Right now I have 2 trucks (details on both coming) - downsized/eliminated the suv some years ago. In general, I care about getting a specific job done, reliability, and cost of ownership. Push the years you own a reliable vehicle beyond 10 and the depreciation per mile is nearly nil. Oh, I'm shocked at how many low mileage trucks are out there.
So, I have 1998.5 2500 cummins, standard transmission, some mild power upgrades done 200,000 miles ago, with 335,000+ miles on the truck today, for my DD. Reliability has and continues to be ridiculously good. I totally trust it - driving it on my present 2 week trip. I'll likely sell it early next year and replace it with a little fuel efficient gasoline suv. Why? because I have a 3500 that does everything I need a truck to do, and around here - everywhere I drive except far northwestern Canada - the price of diesel is well above gasoline. I can cut my DD fuel costs nearly or more than in half with a small gas vehicle.
I have a 2015 cummins, aisin, 3500 CC, LB, mostly used to haul my slide-in camper on long summer trips, but the rest of the year the camper is unloaded and the truck is available for whatever I need. It has 70,000 miles on it, yet only 31 hours idling - it's not downtown friendly. I should note, it had 40,000 miles on it before I felt it was fully broken it - power and fuel economy continued to improve to 40K. I'll replace it this spring. Why? Several reasons: My concern that the smaller fuel tank and lower MPG compared to my 2500 would give me problems were fully realized this summer - I want that 50 gallon tank. I also want to do some suspension upgrades, but they are optional and I see no point adding them to a truck still less than optimal for my long-term use. Lastly, the all around camera system, remote trailer rear view camera, and some other options are highly desirable upgrades.
YMMV of course, but for me - I'd rather have money in the bank than keep working in-order to own the latest technological wizardry that seldom does anything I can't do with a few seconds extra effort. These views have been life-long - well implemented through appropriate 'higher level' education, and enabled me to retire comfortably at 57 - now, well past 15 years ago. In summary, for me, the greatest consideration in replacing anything is cost of ownership, doing the job I need done as opposed to 'nice to have', and reliability. These trucks, with reasonable maintenance, easily and reliably go over 500,000 miles. That's what it is made for and what I bought and paid for - why not get my money's worth from it - and what money I thereby save I use to fulfill other desires.
2015 RAM 3500 CC LB SRW, 4x4, Aisin, BigHorn, 8.4an, Husky-X, Duraflap, cabin air filter, LTX MS/2, Maxiscan MS310, Super Z cables, US Cargo 60K recovery strap. Also 1998.5 NV4500, RWD