I also purchased mine, including using a good sized down payment as well to keep the monthly payment in check. My X7 replaced my previous SUV which I owned for 10 yrs and put 120k+ miles on it during that ownership period. My SUV then and my X7 now will split daily driver duties with my M3 during my X7 ownership and will also meet my family's hauling wants/needs (see my sig pic below
). I don't expect to put too many miles per year on it either, maybe 6-7k or so. Just like my previous SUV, I plan to keep it for the long haul, at least 8-10 years. I keep all of my cars for at least 7+ years and/or 100k+ miles. My M3 is currently at 49k+ miles and 3.5 yrs of ownership.
I would not worry too much about depreciation. I think people place way too much emphasis on depreciation when it comes to cars IMHO. Except in very rare cases, a car will never be a cost effective investment, so I never see it as one. It is essentially a very long term wear item/disposable asset - like tires or windshield wipers. For the SUV above that I traded in for my X7 (2007 Ford Expedition EL, purchased in 2009 w/24k miles), I got $4500 on the trade. After 120k+ miles and 10 years of ownership I feel I got my money's worth out of it so I considered the $4500 trade "icing on the cake". So I treat a car purchase just like any other consumer product that I want - I do my homework, determine what has $$ value for my needs/desires, and I get what I enjoy and can afford.
So as was mentioned above, just enjoy it and get every ounce of value out of it to your level of satisfaction. And when the time is right for you and your family situation, move on to something else that fits your needs & desires.