Just to ad my own positive experience, in 2010 I purchased a used C220 preamp from Ryan. The main output was not working on arrival, and Ryan swapped it out, with shipping at Audio Classics expense, IIRC, for another one, which was fine for a while (the main output did fail eventually, as I think I was over-stressing the jacks with a rather long run of ICs. Since then, I have reduced the stress on the jacks and just use one of the other two single-ended outputs).
After a year, I decided to upgrade the tubes (to Mullard 12AX7 reproductions - a wonderful improvement, btw). Well, getting the cover off these units is tricky, and I lack patience. I ended up chipping the glass faceplate. I called Ryan to order a replacement. He replied that they might have a spare one lying around(!), and if I shipped it to him, he would take care of it for me, no charge! I did send it to him and got it back in perfect shape. Unbelievable customer service, especially for something that was well out of warranty and admittedly completely my own fault.
I don’t buy gear often, but I always check Audio Classics inventory before I do, just in case.