Too bad Bryston does not offer an "upgrade" option where you could trade in your old amp for a 5Ch amp. That would be really cool.
If only Bryston would also warranty their upcoming $12K pre-pro for 20 yrs.
I can see myself buying a $12K Bryston pre-pro + $7K Bryston 5ch amp if both were warrantied for 20 yrs.
I think it's more a matter of not being able to warranty the product due to concerns about parts issues than anything else. A power amp uses parts that are long in the production run, are usually discrete components, and can be substituted if necessary; processing chips and AD/DA converters are not so long in the tooth. Five years ago the best video scaling chips came in dedicated boxes, rather than included with TVs and disk players, but those chips are no longer in production, and nobody uses them anymore in new gear.
Bryston is going to have a certain amount of replacement parts on hand, but AV is a fast moving target. I think they don't want to give you the impression that 10 years from now (think back to 1999) they will be able to fix stuff "for sure", which is what a warranty implies. It's more a matter of "we hope so, but we just don't know".
For the record, Bryston is very good about supporting their products beyond the norm. Bryston hasn't always had a 20-year warranty but once they did start to offer it, there are plenty of stories of Bryston fixing the 5-year warranty versions which were out-of-warranty and no bill for repair. They can do that because they just don't see many come in, in the first place.
With HT gear, a lot of those parts are just outside the manufacturer's realm; they can't keep a tight reign on quality control when they don't have any control over the chip maker. You can test parts and select for quality, but long term you just have to hope for the best. It's just the way the world works now.
By the way, that 2B is a sweet unit. When the ST series came out, they didn't even upgrade the 2B; it already exhibited the same qualities that the ST versions of the bigger amps (3B and up) got with the design revision.