Amp repair...What to expect.

You've raised some issues I never even thought of.
Roland at carveraudiorepair has cornered the market on all
parts, but when I needed service it was a 3 month wait. On the forums I found out that he has former Carver/Sunire people with him and the schematics and such.
I went to Vintage HiFi in Pittsburgh (an authorized dealer and service for many years). Very nice owner, my only worry is the quality of the parts used.

Yes, they are in great demand. I'm sure you've followed the sales on ebay...they are snatched-up very quickly.

anywhere from 300-500 hours to break-in.

It's not break-in it's parameter settling of mainly large signal components such as power transistors and it's not 3 months worth of listening. It's substantially shorter at least audibly. 25...50 hours is more realistic.
Leaving unit on stand-by for a few days will also do the trick.

Mine took 50 hrs. to start sounding like a Sunfire again. Then at about 300 hours, it opened up and sounded like its old self (except that now it was dead-quiet).

I like the DYI spirit in several of the posts.

Just last month I got tired of dropouts on my two Sherbourn 5/1500A monoblock construction amps, chatted with a friendly tech, ordered $2.50 relays, and using my Xtronic solder gun and air tool workstation, some desoldering wick, and high silver content solder, i replaced all 10 relays.

In the process i removed all connector harnesses and applied electrical contact paste to these and the terminals, dusted the heatsinks.

I have been making sweet eyes at Pass Labs and Classé monoblocks for a while, but the 4 of them would be hard to justify (CP-700 biamps) now with perfect Sherbourns.