100% this. This doesn't just apply to mechanics. If any business has wronged you, or done subpar work, why keep giving them your money? If it's because it's cheaper, then you are just paying them to continue ripping you, and others, off. Find someone that does good work and pay for that good work. It's not always convenient, or cheaper, but think about it in these terms; you've worked hard for your money, why give it to someone who isn't going to respect you, or your vehicle, enough to do the job right? Voting with your dollars in every aspect of your life is the way to ensure that we support those who work as hard as we do, and punish those who look to take advantage of others.
I'll get off my soapbox now.