If you have the money, why not go for it?
I like to max out the options and buy the best possible so that it lasts the maximum amount of time.
I last purchased a mac in 2008/2009 and didn't plan on buying another one until a redesign/huge spec upgrade next time. Now, 4 years later, is the next time IMHO, so I purchased.
I won't buy another mac until 2016.
It cost me £3000, but over the space of 4 years its worth it to me. If I bought a lower spec I'd get the feeling to upgrade sooner and I'd end up spending more per year on average than £3000 every 4 years.