I've got two Cygolite Hotshots, one of which is about three years old. They're bright and reliable. The longest ride I've done is nine hours and the one I was using was going strong at the end of the ride. I usually ride six days a week, so they get a lot of use. They're much better than replaceable battery-powered lights for daytime use.
__________________
Regards,
Chuck
Demain, on roule!