I replace and pimp the GPs when I get a car. (I got better things to do on a cold morning, than wonder when & what the PO installed*.)
I have yet to have a GP fail - but if it ever happens, I'm not going to waste my time taking apart the whole kit to find one bad GP.
*My Vanagon had 24V GPs installed, since the replacement engine was originally for a genny and the PO didn't change the GPs to 12V.