With Apple on the cusp of making a major product announcement next week, I’ve had to reevaluate plans to fix up a beloved system in my arsenal that’s showing its age, badly.

Last November I made a switch from a 17-inch MacBook Pro to a 13-inch MacBook. I picked one up after Apple announced the new “unibody” MacBook with a 2.26GHz processor, and haven’t looked back. But the 17-inch model is still part of my life. How much longer it will be, though, is anyone’s bet.

Since I added the petite MacBook to my Mac menagerie, the 17-inch MacBook Pro has been sidelined. It’s gone from the role of daily driver – my one computer that I did almost everything on, from checking e-mail to writing stories, playing games and so on – to an auxiliary role as my wife’s occasional laptop. She’d been asking for one for a while, so it made sense. But how much longer it’ll be able to fill that role is anyone’s guess.

It isn’t a matter of forced obsolescence or caprice. The 17-inch MacBook Pro is still a very capable machine that I’ve kept up to date with Snow Leopard and the latest updates to software applications I use regularly. But it’s showing its age, badly.

After three years of daily use – some would say abuse – the 17-inch MacBook Pro’s case is bent, badly enough that it no longer latches correctly and the optical drive is all but useless – trying to get an optical disc in or out would cause damage. The display housing is a more serious problem, though. A few weeks ago a fissure opened up in the lower right hand corner of the display bezel, and now I see the upper and lower halves of the display housing are starting to separate.

I’ve called around to a few different places and the cost of repair isn’t cheap. Case parts for that model are extraordinarily expensive; rebuilding the exterior of the MacBook Pro will exceed its resale value dramatically.

In fact, I can go to a reseller of used Mac equipped for a refurbished, already-rebuilt MacBook Pro of similar vintage to this model for less money than repairing this one will cost. And if I wanted to spend a few hundred dollars more, I could buy a much newer refurbished 17-inch MacBook Pro from Apple, and get a full warranty (and AppleCare to boot).

We may pay a premium on parts like these because we’re Mac users, but just as a point of comparison I decided to look into what it would cost to repair an equivalent PC laptop of similar vintage, and what I’ve discovered is that the grass is no greener in the neighbor’s yard.

Laptops, regardless of whether they’re PC or Macintosh, depreciate quickly, and unlike PC desktop machines, which feature many interchangeable components you can buy inexpensively, a commodity market doesn’t really exist for generic PC laptop gear. PC laptop manufacturers don’t produce a large quantity of replacement parts, and it’s typically cheaper and more cost-effective in the long run to simply replace the system all together than it is to fix it. So this is one case where, despite what some of my Windows-using friends would have me think, things aren’t that much better for them.

We live in a disposable consumer culture, so I guess I shouldn’t be surprised, but it’s still difficult for someone like me who holds value to something that works. Which is also why I’m still limping along with an HP LaserJet 5MP networked using an Ethernet to AppleTalk bridge, despite the fact that I need to route it through a Mac that hasn’t been upgraded to Snow Leopard yet.

So if nothing else it’s given me an additional reason to pay attention to Apple’s big product announcement next week, and hope that whatever it is, it’ll be worthwhile for me to invest in that product rather than getting the 17-inch fixed up.

And as far as the 17-inch I already own? Well, hopefully bailing wire and duct tape will hold it together for just a little longer. After that? Maybe it’ll become a project machine, like that Windows PC I’ve been putting together. Since 2008.