We also keep our Macs for a very long time. When we no longer need them they are no longer saleable. My yr2000 Pismo PB still has a few uses for us, I have 3 batteries which are still holding in for 45 minutes each. I may buy one more new battery for it. A 3 yr old Netbook is currently our main travel computer, it's a snap to change it's battery. A laptop not having an easily replaceable battery is as unacceptable for us, as a car without a full sized spare.