Yeah, it would be. But I usually deploy Laptop #2 as a testbed server. So the auxiliary computer’s HD isn’t really empty so much as it’s functionality is expendable if I need it to be my main computer while Laptop #1 is in the shop.
I got pretty fast with HD-swapping, although I miss the days of my WallStreet G3 Series laptop where swapping hard drives took about 90 seconds.
I usually replace my laptop after 3 - 4 years. But my wife’s has a desktop that she bought in 1999 (that years, the government was encouraging Y2K replacements by allowing 100% depreciation in one year). It runs XP and she says she will give it up over her hard cold body. She will not consider any of Vista, Win-7 or the forthcoming Win-8. She replaced the hard drive once and it still does whatever it did when it was new.
I was in the same position as you—at least I was three months ago. An iBook with one of the last PPC chips and increasingly feeling left behind. Spurred by an upcoming trip, I snatched up one of the MacBook Air refurbs from the Apple store for $700. Solved all my problems: fast, modern, weighs only 1 kg, a beautiful object from the future. At home it gets a big monitor and regular keyboard, but I can also grab it and put it in my smallest backpack. Hell, it’ll fit in some of my coat pockets. I did grab one while Snow Leopard was still easily available because I’m tied to some software (FreeHand) that won’t run on Lion.
I can’t answer the general philosophical question about when to buy a new computer. But if you’re still using a Mac with a PPC chip, the answer is much simpler. Now.
Any shop can load XP onto a new system, I have done half a dozen in the last year for people who needed XP environments for stuff. Not always easy to find drivers but usually enough for the application in question.
A couple of goodreasons… usually when I start having difficult controlling my urges to do something like that is when I get a new one.
Have to say converting to Mac definitely saved me mucho brain cells.