Class A amps run hot! And it does lower there life expectancy. With that said if you dont mind the heat it gives off (like some of us that live in Texas do) and you dont mind sending it in after a period of years (it will be needed) then go for it! :-)
P.S. I have a old ADCOM GFA 555 that is class AB and it still sounds awesome today after 30 years because it runs cool to warm never hot like fry an egg hot that class A amps get. Im not comparing the sound, of course the Krell or Mark Levinson amps do sound better but at a much higher cost. If I were the OP I would ditch the idea for a highly investigated and informed used McIntosh amp and be done with all this "amp runs Hot, Class A, send in for service" talk. Find a special amp that MAC makes, do some research, they do make some great amplifiers (its what they do best)
Matt M
P.S. I have a old ADCOM GFA 555 that is class AB and it still sounds awesome today after 30 years because it runs cool to warm never hot like fry an egg hot that class A amps get. Im not comparing the sound, of course the Krell or Mark Levinson amps do sound better but at a much higher cost. If I were the OP I would ditch the idea for a highly investigated and informed used McIntosh amp and be done with all this "amp runs Hot, Class A, send in for service" talk. Find a special amp that MAC makes, do some research, they do make some great amplifiers (its what they do best)
Matt M