As others here have said, 7 years is nothing for solid state gear, and Bryston is extraordinarily well made gear. That said, there is a chance that you may not be imagining things -- I have a 10 year old 4B-ST, and a couple of years ago, I noticed something wasn't quite right -- it sounded like one channel was louder than the other. Seeing as I live a couple of hours drive away from Bryston, I drove out there, and Mike took all of 10 minutes to figure out that it was the balanced/unbalanced switch at the back of the unit that was at fault. It took him another 15 minutes to replace it and then he hooked it up to the test gear and reran the bench tests to ensure it was within spec. The amp tested out virtually identical to the original spec sheets.
The moral of the story is that even with very well made gear, sometimes something stops working correctly. This is *exactly* why I only buy bryston for audio gear -- Not just because it is the best, and not just because it is outstanding value, but also because in the very unlikely event that something does go wrong 10 years down the road, you can count on them to fix it quickly, thoroughly, and professionally. I don't think you'll find a better company to deal with in high end audio, or probably any industry for that matter.
-- Ian.