I think if you use a quality crimp connector by 3M, etc. then you shouldn't have any problems with them coming loose. I have used the 3M connectors on my pins, and numerous cars I have worked on and never had any problems, even on the starter solenoids (mounted directly on the starter) on some cars, I have never had a problem with a quality connector coming loose, and I think the vibration of an engine would put more stress on a connector then a pin would. I think connectors are like ic sockets, if you use the cheap off shore stuff made of the mystery metal, then you will have problems, but if you use the good quality brand name stuff then you sould be ok.