Amp longevity, if well taken care of --the risks of purchasing used equip.

My GAS Ampzilla that I built from kit is still my working backup amp and is 51 years old. Still sounds great (after two rebuilds).

Many years ago I bought a pair of speakers at Stereo Exchange in Manhattan. Dave Wasserman, the owner, mentioned that the speakers sounded especially good with Conrad-Johnson amplification. I told him I was using a pair of McIntosh MC60s, and an Audio Research D51 amp as a backup. That drew a huge guffaw, and he said “I love a guy who’s got a backup amp. You clearly don’t need the CJ gear.”

I’ve had the Macs since 1979. They were manufactured in 1959 and 1960. I’ve had only two problems over the years, so I probably don’t need the backup, but I do sometimes swap in them D51 for a different flavor. The D51 probably dates to 1971 or’72, and I’ve had one issue with it. So yeah, older amps can be quite reliable. But I don’t know anything about Bel Canto. 

I purchased my Mac MC240 (circa 1967)

around 1995. Still going strong making wonderful music. 

The parts that age soonest seem to be the caps. Inspect them for swelling and discharge. They can also be measured with a multimeter. 

Caps are relatively cheap to buy and not difficult to install. 

If you are somewhat handy with a soldering iron it's a fun way to really get to know your amp. 

I'm running a pair of MacIntosh MC2100 amps that were manufactured in 1975.

Other than a recap and general cleaning I have not had to do any other work on these - and no problems with them either.