Here too...We use mostly aftermarket parts across the board and have a fairly low part failure. on top of that we make sure that who ever our main vendors are pay the complete labor dollars that we charge to the customer. for instance....if we replace a wheel bearing for $275 labor price...we make sure I vendor credits us for the part and pays the full $275 in labor cost.
We who run our independent repair shops have only our reputation....so IF we have parts failure comeback, we pay for a rental, give free oil changes for inconveniences and so on..that can easily cost more than the $65-$100 labor rate... so we say, if the vendor CANT pay a $200-$300 labor claim once every 2-4 months...tell them you will find a parts vendor that will gladly pay those labor claims to get your $40k to $75k or whatever it is you spend with them. that's what we do....
That's just my opinion.