I've had Oxford heated grips on my C14 for about three years, and they work well.
I put a pair on my Versys last year that I bought at Cycle Gear that looked very similar to Oxfords, and they also work well.
I have had the touring Oxford grips for a year with no issues. Side note: I left my heated grips on yesterday morning after my commute with out realizing and they shut off automatically by the time I realized it. Bike started fine after.
Realistically, how long should I expect them to last?
I've had a few pairs on a few bikes. If I remember right, once I had a controller failure, and Twisted Throttle shipped me a replacement free.
On my Versys the grips have been on there for 56k miles or so. I think they would have worn though long ago, but I wrapped them with tennis racket wrap. I think that's key to making them last: don't wear out the rubber.