Preventative Maintenance will always be higher on a older truck compared to a newer unit, but like snowman said rubber ages out and metal rusts, nothing lasts forever, I was a VW/Audi tech for years because those German cars could keep repair shops open forever by themselves lol. The biggest problem for all makes and models is how much electronics they are packing into them now
With that said yes those X5's are great SUV's. Smooth, fast, fun to drive even for a big truck, but I you said it best, I'd be wary of owning it much longer than 100K
get a new one every couple of years lol, good to go. A buddy of mine has a Porsche Macan Turbo that he's had for about 4 years and swears up and down its been more reliable than his pervious Tahoe. He forgets I'm the one that does all his Maintenance