Some really interesting comments. I think a theme is developing, the scarcity of parts may be the major decision factor. As cars get more electronically complex with lots of circuit boards and hundreds of chips, any that are unique to that vehicle will only be available so long. I don’t know if mechanical parts will be as much a problem although some critical parts could be. Currently I’m not sure we can find new nav computers or DME modules for our vehicles, and resellers with reman units may get hard to find as well. I think this may be the Achilles heal of vehicles of our vintage, and you can only wonder if the timeline for obsolescence will shorten proportionally with later model cars. This is a sustainability issue that EV’s won’t solve with less carbon footprint, as US manufacturers push for 16MM vehicles a year and third world countries have exponential sales growth.

IMO, the law of supply and demand applies. As long as there is demand for parts there will be supply. Perhaps as demand declines a few suppliers will buy up available used and new parts but I don't think that will happen. I don't think even the most rare of stock X5s will ever appreciate in value. The annual cost of maintaining an X5 is certainly not cheap but it is dramatically less if one is DIYer. I wouldn't own a 20+ year old vehicle if I wasn't able to fix it myself. Labor costs won't be decreasing and have passed point of reasonable for a vehicle that is in the resale range of E53 and E70 X5s many years ago. I bought my X5 new and have not experienced anywhere near the repair costs listed here.

BMW still sells new M54's, or rather they are remanufactured by BMW so you know that they'll be good as new.

I'm surprised folks are saying X5 parts in short supply. Yes, some body parts are difficult to come by such as towing kit, 4.8is body kit, OEM head unit etc. But wear and tear items are always available, even for my old 1997 528 E39. I've never failed to find OEM or otherwise maintenance parts.

Are you sure? I've been told by several mechanics that they are not available at all.

I don't know whether the former is true, but I can tell you that you are absolutely making a false assumption about the latter. The quality of Genuine BMW parts have declined dramatically over the past decade. I've received counterfeit parts (only once, but still), Victor Reinz (trash), and parts that flat out were made wrong all over the counter at dealers.

BMW subs out engine remanufacturing to third parties. Don't assume that it's getting done to in-house standards.

When I find a 4.8is that I like ;)

All mfgs. purchase (made to their specifications) parts from outside vendors even for new cars. Only issue that I have with BMW parts is the pricing. I have had no issue with purchasing OEM parts either. That said, I don't purchase enough parts to draw any conclusion either way.

I've been buying BMW parts for a couple decades now, and what I can tell you is that there was a definite inflection point about ten years ago when quality started to decline. I've bought a LOT of parts. As in the guys at my preferred parts counter know my voice on the phone levels of a lot of parts, and that doesn't include the other vendors I buy from.

The key is not that BMW is subbing things out to third parties. It's that BMW clearly cares less about what they're subbing out than they used to. BMW just buying known trash Victor Reinz gaskets and selling them as Genuine BMW is a good example. There are also many examples of BMW selling parts for older cars that were clearly never tested on those cars. E30 M3 bumper brackets that didn't fit come to mind. Or the E30 M3 spark plug tool that didn't fit in the spark plug hole. (lol)

How do you conclude based on your individual purchases of parts that BMW cares less about quality when based on one gasket, a bumper bracket and a spark plug socket?

MFGs don't redesign parts for old models. They use the original design specs and purchase from the same sources or one that meets their quality criteria and specifications. Parts are a major profit center for a MFG. Not one MFGs are careless about.

Did you use the gasket and it failed?