Yeah, at about or below 60 I decide that I probably need to wear long pants instead of shorts under the Darien pants. I usually put on a long sleeve shirt over my tee shirt and try to remember to have a fleece vest [not electric] with me, too, in case the weather turns cold on me. (Of course, I always have lightweight long underwear [Patagonia Capiline] and heavy wool socks in the tank bag year around - just in case the weather turns really nasty . . . . )
I'm going to try the wrap-on/removable grip heaters from RiderWearHouse and see how they work out on the FJR without V-Strom hand guards. I use them on the BMW, as does my wife on her bikes, and often need to switch them off for a while to keep them from being too hot. There is some loss of fine control with the overwrap, but I'm not pushing that hard in cooler weather anyway. Seriously, the fact that the FJR has the ambient temperature readout looks like a good safety device to help me judge at what point I need to start being concerned about ice forming on the road out on the passes.
I can dress for the cold, but am not willing to dress for ice on the roadway and going down that hard at highway speed.