Wife has the Hestra Power Heater Glove. She loves them. She has an issue with cold fingers. They do warm all the way to the finger tips. They have 3 levels of heat that can be set. She has used hers on 3 (high) and 4 hours without issue. Set to 2 stays warm all day which includes the day skiing and use that evening after skiing. She probably used them 10 times on the slopes last season but more during the evening. I would say all 10 days were normal skiing use. I can't remember but I think I got them at the Ski and Snowboard Expo in Denver. They were on sale for a really good price.
They were on the list of things I'd never thought I'd own, until I received a pair of Hestra's as a gift. I actually really like them. The heating elements are in the fingers and do a really good job of keeping my hands warm. When it gets really cold (sub zero) I'll still grab the big arctic mittens with hand warmers - between the cold temps and the gloves cranked up on high, the batteries wont last the full day. No problems with the battery lasting on the on the medium setting, but the cold can still be an issue.