The only way I would ever buy a "new" car(besides a good lease) is if I was planning to keep the car at least 2 to 3 years after its payments are done. I would never finance over 48mos unless it was an attractive 1.9,2.9 rate. remember there is nothing like a free and clear car(Well maybe a free and clear house)
. I love a good deal on a lease, but once you do the math they really aren't that good anymore.
The depreciation curve on most cars starts to even out at around 24 months. That is why I always look at 2 year old low mileage cars, if you can find them. Plus most are still under MFG warranty for another year.
http://www.planetporsche.net/porsche-sales-leasing/32241-what-does-cayman-depreciation-curve-look-like.html
good luck and let me know if you have any questions on the subject. I have been out of the business for a few years but the mechanics of it haven't changed much.