I had one in my old Berg for over 2 years without any dramas but a couple of weeks ago I had a main fuse blow on my bike, it was full of mud and dirt so I replaced it, rode for 3 days without a drama then on the 4th day the bike just stopped while I was riding along.
Still had power but not enough to run the electrics, the battery just shat itself, replaced under warranty (it was about 6 months old)
I guess like anything sometimes you just get a dud.