I'd like to give a big thanks to all who have read and commented on this thread, y'all have been great. Like all good things, it must eventually come to an end. She's up for sale now:
https://xoutpost.com/classifieds/bmw...-6is-sale.html
I've put a lot of thought into this and gone back & forth a bunch of times on whether I should sell it, but I think it's for the best. I don't drive the X5 much anymore, since I greatly prefer my 2000 540it for daily driving duties. I also want to free up some space and money to pursue other cars. I'm happy to say the X5 has no major issues as of right now, so I feel pretty good about selling it knowing that it should work reliably for many years to come.