Until the end of April I have the opportunity to get a significant discount on a near maxed out 2009 8 Core Mac Pro. Obviously there are several variables, but is there a general rule of thumb of average depreciation for a machine like this after 1, 2, or possibly 3 years? If I decide to go ahead with the purchase I'll more than likely upgrade in 2 years, possibly 3. Thanks for any insight... ....I know this is a pretty general question, but I'm looking to retain about 50% of the retail value in 2 years. If I could do that it would be financially worth it to me for the added convenience of working from home (from time to time).