Well, not sure about in 1989, but in the mid 90s with the revised play it loud series(not pocket) I got well over 10 hours on 4 AAs. Not sure if the play it loud series had any differences besides cosmetic though, and I'm not sure how much battery technology improved from 1989 to mid 90s.(though I was using just regular old alkaline batteries, surely they had those in 1989?)