Servicing amplifiers from very small companies?

A lot of us buy amps/preamps from what are virtually one-person operations. In general, can these be serviced if the company shuts down? How easy is it for a skilled service shop to deal with a unit with which they are not familiar, even assuming all the parts are available (and is even this a good assumption?).

(I don't even want to ask about speakers or CD players/transports, as I don't think the prospects are good in those areas, but I was hoping prospects were brighter with electronics with no moving parts.)

I know this question has come up with Shindo in relation to parts, but I thought I would expand it.