When to get your amp up graded caps ???

Since the op just bought the amp, Breuninger.. How do you know it has not already been done? The automatic: "go spend money" seems a bit over the top? Having it checked by a competent tech, or by MAC, (which is certain to not just change them to get some cash in hand) is a worthwhile idea IF the op is really concerned. Otherwise it is not much of a problem.
Calling it like Russian Roulette is a little over the top dude.

Russian Roulette requires 1 live chamber, otherwise it's just too dangerous.

The consensus is that power supply electrolytic caps should at least be considered for replacement when they start to get up in age. But, that really is a generalization and it really depends on the source/quality of the parts. I know a current builder that looks for certain older parts, including electrolytic caps, because he likes what they do in his designs. I am thinking of getting a linestage from this builder, based on an in-home audition. None of the parts, including the electrolytic caps are any younger than 50 years old and some parts are much older.

Some of these parts, made by such companies as Western Electric, command quite high prices on the market today.

"The consistent age for amp caps has been twenty years. Ten years no way."

That's your opinion kind of like dip switches in phono stages you stated have a 12 cycle life before their done but certainly not based on expert knowledge and design such as the people who actually build and design them.

They may appear to last 20 years but the 10 year's is based on when they will typically begin to degrade. The idea is to maintain the amp at optimum working order as it was new. Having the amp cleaned and biased to spec in all parameters prior to decades of use and if replacing the caps at 10 or so years will do that and that's the wish to do so well that's what it takes.

The idea is not just to sell more caps it is to keep the amp working optimum period. It's not to say it would not sound good still to a new owner not knowing what it would of sounded like new. The op was curious enough to ask and even the seller was not specific on what was done and gave him a general answer that still did not answer his question. I think Reich and McCormack would disagree with you but hey what do they know.

I agree that having it gone over by Mac themselves and getting their expert opinion and original parts if needed is always the way to go. If your happy with it and it sounds good leave it be if that is your choice. If you want the amp to maintain it's original sound then as the op was inquiring as he obviously was interested in that then have it gone over , biased and brought to spec with new caps. Why not keep a Mac functioning in as new condition.
How long will you keep those Bryston amps's before you send them back to be checked over. Wait till just before your 20 year warantee is up or take advantage of keeping them peak performing while your enjoying the 20 years they offer?

Cheers

I never had a problem with my Forte 4a and i had it over 17 years before i sold it. And I only sold it because i had a pile of money to burn on new stuff. I plan on the same for my Bryston. 20 years? No problem.