I did something I will not classify as a mistake, but I will never do it again. Beware! I leased a new car for 42 months. My research showed this is the most profitable term for the leasee. My plan was to buy the car at the end of the lease so I opted for the lowest mileage allowance knowing there would be no penalty with me buying the car. All of that was just fine, until it came time to finding financing for the buy. I learned the older the car, the higher the interest rate and the shorter the term. My finance payments were a bit more that my lease payments!
You mentioned a 10 year term, that is rare, and usually requires a car of $100,000+. Terms of 3 or 4 years are most common, 5, 6 and 7 years are possible for newer cars, again older is shorter. For some years I had both a leased car and one on purchase. At that time I was easily able to fully deduct the lease for business. Rare are the people who can fully deduct all lease costs of a car that is not solely for business, the difference is lost. If you have two cars you can pay for less miles on your lease. Don't be too afraid of the mileage allowance, you can calculate the cost of adding 10,000 miles before you sign the lease and the number will not stop you heart.
My current plan is like a lease in a way. I keep and drive my cars for +/-10+ years. I usually buy +/- 5 year old luxury cars. If you shop well you can find good deals at the luxury car dealers who know who will be bringing in what off of a lease. They will work with you as they know you're looking to buy. If you credit good you can get a low percentage and payment for 5 years and drive for 5+ years paymentless. I just bought a 2010 Lexus with 56,000 miles in near mint condition; which was a wife's car from a couple who have been buying Lexus from the dealership for 25 years, full service records, 37 mpg and no wear or tear. In closing, most people who are leasing shouldn't be. Buying is better for most people, unless you are flipping 20+ properties per year and have a large enough cash flow to make a lease make good sense. Do not leave your accountant and tax man out of the decision, they are ones who have to grind the numbers and will be best able to tell you your best deal. Good luck its a question with no answer! LOL!