I use SS lines at work all the time on vibrating stuff. No hard vibrations. I'd say they are just about the same as my 750 vibrations. We havent had any trouble with fatigue. Granted the lines are at 450 F to 650 F for fuel vaporization allowing for more flexibility, but the system has been running on and off for 4 years and no problems. We have a coil in one of the lines, but that was for cooling so we wouldnt burn up the gauges.

Im going to run hard lines on my bike and I might put rubber at the engine because I'm only running the two lower motor mounts and it might end up torquing a bit under hard acceleration. I dont want to kink a line when that happens.

Some of these swagelock fittings will come loose because its just a compession fitting, but in my experience, it takes a lot of shit for that to happen.