Mac Pro 1009 days (almost 3 years)
Appalling!
The desktop/laptop realm enjoys a great amount of freedom in that most everything works well and there just aren't a lot of features that Apple is ready to compete on. They aren't going to win with gaming, they aren't controlling enough of the market to battle for niche programs, and the major software suites they do have run pretty damn well on current hardware.
It would be a numbers update only and I just don't really see a lot of reason until Apple starts doing something to justify the numbers. Youtube and Facebook can only load so fast for their users.
a) There are machines with better spec'd hardware from other vendors while Apple sits around doing nothing or close to nothing for a few years.
PLUS
b) At any point in time, there are people with older Macs who'd like to upgrade to the current state-of-the-art...or more importantly, to get the best bang for their buck.
PLUS
c) Apple continues selling older hardware at the same prices and does not reduce prices over time until it releases a new model, which could be several years later. This makes the hardware overpriced compared to non-Apple ones.
The above combination of factors make it quite hard to justify expenses on older hardware for a good number of Mac users (as can be seen on various forums) who're invested in the Mac/OS X platform and wouldn't want the hassle of switching to Windows or Linux. It thus creates a lot of fence-sitters who keep refreshing the Macrumors Buyer's Guide regularly and hope for something to happen.
I would think though that in most cases, the persons considering a Mac are rarely looking at the specs to make the decision - Apple hasn't tried to compete with specs for a long time, and instead relied on word of mouth and OS X to carry them. Maybe a refresh would help make that a bit better, but I also feel they're stuck in a bad loop where because of how long it has been since a refresh for some devices, they need to really release something crazy good for the price to avoid the ire of purchasers.
https://www.dropbox.com/s/hgury35bsickbvu/MacProProtest.jpeg...