I have a 4-yr-old PB that's more or less been on and in use for the entire time I've owned it. Never had any problems. But in a few days I'll have an iMac, and I'll only need the PB very occasionally - it will be off most of the time. I don't want to sell the PB for various reasons, one of which being the possibility to be portable once in a blue moon, when I need to be. I'm planning on stripping the PB down to the bare minimum so that it runs a bit snappier. So what I wonder is are there any disadvantages to the machine if it's left off most of the time, and only occasionally started up and used? The question sounds stupid even to me, but it occurred to me that I've never had a computer that hasn't been on most of the time. I'll use setup assistant when I get my iMac, so the data on my PB won't be lost if something does happen to it.