I may be the odd man out here but hear me out. Buying a machine that is quality to start with I think in it's self will hold value. But here is where I stray the idea of buying something so its worth more at resale doesn't hold much water, maybe for a business or guy that is buying a new machine every other year, but in general when you start thinking about it logically not sure there is much merit.
Now when I say this I am talking about buying new and then selling it down the road. Because there are guys that will jump on here and say bought my tractor 10 years ago and just sold it for the same price, but what they don't tell you is they bought it used, yes it matters.
But for starters I never buy anything or maintain an item for the next guy, I buy what I need and want and take care of it because that is what I want. Like I said buying something of quality will mean it will hold up and that by its self will maintain value. The next thing to think about is by the time you factor in purchase price, maint cost, insurance, operating cost, inflation of dollars, most of the time you are going to lose money, you just will. Also when you look at guys numbers at times in terms of what they said they bought it for and sold it for, their math doesnt work out. You will see things like I bought by JD for 20k in 2000 and sold it for 12k this year, and are happy about it. But the guy that bought an off brand bought the same kind of tractor for 15k at the same time and sold it for 9k. Well yeah the JD made more money but it also cost more money up front so there was no doing better there.
Bottom line is this you buy a recognizable quality machine and take care of it, resale will take care of its self. Worrying about its value 20 years is illogical, as the cost and return will be so convoluted at that point. TBH I dont like throwing my money away but something that is 20 years old, at that point I would be happy to just get rid of it. Now if it is something you plan getting out from in 5 years or less, taking a closer look might be worthwhile.