It could have failed. For me my cordless phone returns to it's charging base and no phone call lasts 6-7 hours so your handset would be fine for my use. Is there some reason you are not returning it to the base?
Bob
Hello,
I have the aforementioned cordless phone and the following problem.
After I charge its batteries then it is working for about 6-7 hours and then all of a sudden
it shuts down. When I turn it on it shows that the batteries are discharged and it shuts down again.
I have tried new batteries but the same problem appears. What could be the problem?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic