I've been riding Gerbings heated clothing since the Mid 70's, when they first started in business. I currently have the latest and greatest and still carry an older jacket as a backup. I have the full catastrophe of their liner line - jacket liner, pant liner, insoles, gloves.
Generally speaking, it has to reach pretty extreme temps for me to use the pant liner, insoles or gloves but I put the jacket liner on under my 'Stitch when temps get down to about 60 or so. With the new 'filled' jacket liner, I don't need heat until it gets below 50 or so. Regardless of the outside temps - my bike goes nowhere without at least the jacket liner. I currently run the permanent dual controller mounted on my RT and carry an old Heattroller as a backup. I've never had a controller fail.
Oldwhatshername and I have ridden a lot of miles two-up with us both plugged in and on, with no problems on any RT since 1993.
In years gone by, I've had one jacket liner that had some heating issues after about 5 years of use. Gerbings simply handed me a replacement.
I can't speak highly enough about Gerbings heated gear, the people I've dealt with over the years, or the company and its support of their product from day one.
I wore Gerbings heated gear every single night and several days during the 11-day, 11,000 mile Iron Butt Rally in 2011. I stayed nice and toasty warm and comfortable the entire ride.