IBM Thinkpads have a cult following in part due to not just a good design out of the gate, but the fact that the original designer refused to bend to pressure to change the design every year. The parts are interchangable to large extent between models spanning what, 3—5 years? The guy was under constant pressure; was told to give consumers something fresh by changing up the design. Luckily wisdom prevailed and he disregarded such reckless advice by responding with the mantra: ”if it ain’t broke, don’t fix it!”
I’m happy to buy Thinkpads over 15 years old, often sold for ~$10 on the street, because if something is broken or breaks it can still be used for parts to fix other models of Thinkpads from roughly the same decade.
Lenovo acquired Thinkpad from IBM and gradually fucked it up around the T410 or T450 models as they gave in to the demand of consumers giving a shit about shaving off every gram of weight possible at the expense of ditching rugged rollcages and ditching features like optical drives. Watch some videos of people trying to simply remove a keyboard from a T450 to see what I mean.
Whirlpool also has a reputation for not radically changing the design of internal components. I called a repair shop over a washer or tumble dryer that was like 15 or 20 years old. They said at that age, if it’s not Whirlpool they won’t even show up because when the parts change every year then spare parts quickly become unavailable (of course before people start needing the spare parts). They said Whirlpool is an exception because the same parts will be used for a decade or more, which then justifies the business of making spare parts for a prolonged time (I imagine as well the aftermarket likely thrives too).
Grain of salt though because I heard Whirlpool doesn’t always put their label on their own products and Whirlpools also end up getting labeled as Sears Kenmore. If Whirlpool rebadges something else as Whirlpool, how could the design have consistency w/other Whirlpool machines? Anyway, it was just an example and possibly flawed based on one repair shop’s opinion.
The problem -- no metrics
This is all just tribal knowledge propagated ad hoc by word of mouth. The masses don’t generally know this shit and probably most of them don’t care. I think Whirlpool and Thinkpad were not even diligent enough to advertise it. Maybe they did not even know in advance they would have design consistency over the years. Perhaps if they advertise: ”uses the same motor as previous 6 models”, they would fear that it would chase away foolish consumers who would regard that as ”old”, unevolved, or non-innovative. Those same stupid consumers who are brainwashed to chase “latest and greatest” are why we face so much unrepairable garbage on the market.
Since no one tracks design stability/consistency over time (not even Consumer Reports or similar orgs), there is no incentive for manufacturers to try to satisfy the unknown & unmeasured demand that no one is looking at.
I think about this a lot. When a company updates a design, they often don't have "release notes" on what actually changed. Sometimes they swap out components for cheaper stuff, which they won't tell you. Sometimes they fix some stuff that was bad from the original design, which they often won't tell you. The only time they tell you about updates is if they are just making something presumably better, but that also doesn't let you know for sure if parts will be compatible.
Some brands keep the same product name, but make lots of changes, and some brands make essentially the same product, but change the name (e.g., vitamix 5200). Sometimes model numbers help, but they don't always show you the model numbers, and oftentimes retailers have their own model number that you'd have no clue is the same. I often end up having to rely on stuff like the wattage where if it changes, you know something changed.
I have a tool (milwaukee circular saw) that started getting an intermittent failure. When doing some reading to try to fix it, I found the schematic and parts list for replacement parts (Milwaukee is good about this). I then found the same list for the newest Milwaukee circular saw (i don't remember if it was the same model number or just n+1). The only replacement part that was different between them was the switch that sits behind the trigger. Enough people must have had the same exact issue that I did that they changed parts, but you would never see that information somewhere. The issue ended up being that the switch design created arcing that fouled up the contact surfaces, so you could technically just take it apart periodically to clean them, but that was a pain, so I just sent it in to have it fixed with the new part since it was under warrantee.
That fault is common in vintage stereo amplifiers too. A popular mod is to install a triac so that the switch becomes basically a soft-switch toggling a few hundred milliamperes, rather than the full current draw for less arcing. See https://audiokarma.org/forums/index.php?threads/is-your-unobtainium-power-switch-worth-5-and-an-hour-or-so-of-your-time.504673/ for discussion; not sure if it can be directly applied here.