I'm not sure exactly how long I get from a full charge as it's never gone from full to empty in one sitting, but it's a lot more than one hour, maybe five or six hours.
When I practise it's usually for about an hour to an hour and a half and I get a good few sessions out of it before it needs charging.
Kind of intrigued now as to how long it does actually last.
Mine is the mp-2 rather than the pro but I can't see there being that big a difference.