I used this for almost two winters before the battery vibration feature wore out. It still runs for a solid hour on high, down from 3 when I first bought it. It adds an hour or two to my surf sessions. I spend $25 in gas every time I surf so by doubling my surf time this thing paid for itself in the first month. I am ordering another one. Winter surf is not the same without it. The placement and design of the battery pack and switch could be better. Sometimes when I take a hard wipeout the vest gets shut off or on. Fumbling with it in the water is a pain. But it's nice to be able to fire it up if the wind kicks up or just towards the end of a session when you need it.