Year 2 Experience with UpStart Replacement Battery???

Have always bought models using AAs, so I'm new to Canon's proprietary batteries.  Checking eBay for a second battery (NB-6L) I came across "UpStart" brand that's a little pricier than other knock-offs but less than a retail Canon OEM replacement.   They have a nice web site and offer a lifetime warranty - certainly looks a notch up from the usual knock-off China battery.

My experiences with knock-off batteries has been uniformly pathetic after a few good months.  So apart from any compatibility problems, I'm not much interested in first week performance with UpStart.

I would very much appreciate learning if these batteries compare with OEM hold up for a couple of years as I'd expect from an OEM battery.  Also any any experience with their warranty would be a bonus.  I'd imagine this could assist others, since most users end up buying additional batteries.