I have been usinfg these for about 2 years now with absolutely no callbacks or problems. The difference in these Wago connectors and the switches and receptacles is that Wago uses a spring steel retention spring and a tinned copper contact whereas the switches and receptacles use a brass retention spring and brass contact. I use Wago connectors based on the same principal on circuits up to 100A on motor controller cabinets. Even if the cabinet heats up, shakes, wires get pulled, or the conductors hop due to inrush currents they stay as tight as when I put them in.
I don't use them on stranded wire due to marginal success, but give the 224-101 and 224-112 lighting connectors a try. They're so much faster than wire nuts for fine stranded wire.
Also note that they're all UL Listed for 20A service and can be used with alum. wire with the addition of Wago's "Alu-Plus" compound...
