I booted up my Thinkpad 760 XL from 1997 recently and let it run for a couple days. My WinZip was more than 9000 days past expiration, and it counted up one by one, the number just spinning ever upward for the better part of half an hour. 2 of the 3 batteries I had for it still charged to above 90% and drained at the normal rate, so I could still run it unplugged for around 6 hours. The batteries were modular, so you could have a cdrom, floppy, or battery in the first bay and a battery in the second bay. I normally ran it with 2 batteries and an external pcmcia cdrom that ran on double-a's. For a 28 year old laptop, it was still incredibly usable.