Dekion, keep your car for like 3 years (or 36,000 miles).  Just have lots of fun with it, put some miles no it, then give it back.  I would say to get the new 3-series 1 year after it comes out...that is usually when all the kinks and little problems are worked out.  And as we all know, BMW has a tendancy to release their cars a tad too soon, which gives early owners lots of headaches.