Mine was not a warranty repair, it was actually elective surgery I sent her in for😁. I have a Simaudio Titan 5 channel amp that is 20 years old. I bought her used a few years ago. Though she was super clean and sounded every bit as good as I had always dreamed, it was a 20 year old amp. I contacted Sim HQ in Canada and though the rep stated they "overbuild" their amps and that "every single Titan is still out in the field" it would be a good idea to send it to them for cleaning and calibrating. This was at the very height of Covid when literally everything was shut down and you couldn't even get in to Canada. The rep told me about 4-6 weeks. It ended up being a little over 8 weeks. But again this was at the very height of Covid so to be expected it would take longer I guess...And mine was elective as I said.
Your situation is different, and yes this is bad communication/service. BUT take him up on the loaner! I ended up buying a Monolith 5 channel ($1299 at the time so I figured why not?) to fill in. Though this amp was nowhere near the class of the Titan, it did get me through. The silver lining for me was as soon as I got the Titan back and connected her I was truly truly awestruck! I think a lot had to do with it really hit home how different amps can sound and what an affect a higher end piece of gear can have on your system. Made me appreciate the Sim all the more...
I ended up returning the Monolith and got a full refund!
Best of luck my friend...