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

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.

Normally, 10 years old is nothing for a quality amp...  Using older Vintage amps periodically can save the caps.  Especially, if they were high quality, long lasting caps to begin with...  Amps that sit for decades can have the caps dry out - even high quality ones....   If you are worried, you can ask for very detailed pictures, so, you can do a visual check of all the caps to look for swelling or leaking on the boards and you can check the reputation of those particular caps. You can also ask for a picture of them checking the DC offset on the speaker terminals with the amp on....  This is a super easy check and you will want to see the DMM display and the amp connections in the picture.  The lower the DC offset voltage, the better condition the amp is in.  The first time firing it up, you also might want to use a Variac. 

Checking the DC offset on an amplifier requires a digital multimeter (DMM) to measure the small amount of DC voltage present at the speaker terminals while the amp is on with no input signal. Ideal DC offset is close to  0 mV with readings under 20 mV — 30 mV being considered healthy and safe for speakers

I wouldn’t worry about it. I’m using the same ICE module but not the Bel Canto case. Still works great.

mk1 is basically just the module. You can find D-Sonic amps using that module for 1/2 the price.

The replacement module can be bought here $400:

https://www.parts-express.com/ICEpower-1000ASP-Class-D-Audio-Amplifier-with-Power-Supply-Module-1-x-1000W-326-206?quantity=1

I have enjoyed most of my gear for years, to decades. I have also bought most of my gear used. I particularly had issues with a YBA CD player, which went for repairs twice in the 20 years I owned it. Rubber belts. To be expected. 
I had an ongoing issue with an AR LS15 preamp. The main problem was mostly an unscrupulous dealer. I paid to have a problem fixed, and they insisted on installing new tubes. A month later, same problem. I took the unit to a 2nd shop for repairs, and to my total surprise the 2nd shop told me the pre amp was totally full of dust inside ( obviously had not be cleaned by the first shop ) and that the tubes that were installed were total garbage, with a crazy amount of background noise. I wasn't sure who to believe.  I am still using that AR LS15 daily with the 2nd set of tubes installed, still sounds great, likely 10 years later. The first dealer scammed me.  The first dealer has since gone out of business. 
My take away is this, take it to a repair depot, not the dealer. Quality does matter. There are bad designs out there. If a circuit board is bad, there is a good chance it can not be repaired.  If it is a bad component, that can be sourced and replaced, in a well designed piece of gear, go for it.

I purchased my Yamaha RZ-Z9 new in 2003 and it has over 35,000 hours and still plays just like new.

...Maybe the fan is a bit louder.  Never been serviced.