Sony-Eric HBH-65 standby time

Hi,
Is there anyone out there that can tell me how much standby time I can
expect from one of these units?
I am trying out my second one within two weeks and I get only 6-7 hours
standby time from them with no other activity i.e. calling or receiving. I
fully charge the unit for 1.5 hours. The first unit I charged and
discharged completely about 5-6 times and no improvement of standby time.

Thanks,
Blink (Chris)