I can't beat James's 1974. But I'm pretty close.
I've been a very happy Bryston customer for just shy of 33 years.
I bought my first 4B in January 1979, at which time I wrote to Bryston - a real letter, of course, not email - asking a number of questions about my new 4B. I received a helpful letter from the company's senior engineer, Chris Russell, who has since climbed to the top of the Bryston ladder. I was impressed with that kind of responsiveness then, and have kept his letter as a reminder of just how good Bryston is in terms of its customer relationships.
My first 4B had a 5 year warranty on it. I discovered some years later that Bryston had extended its warranty to 20 years. And then I learned that the extension included previously purchased equipment, which meant that i had many more years of warranty coverage. More importantly, I learned that this was a company determined to earn and win the hearts and minds of its customers through excellence in equipment, integrity, and fairness - something extraodinarily rare in modern commerce.
Chris's letter proved to me that Bryston would be there when I needed it, and that, together with the performance of its products, instilled in me a degree of confidence that prompted me to buy more Bryston. Altogether I own or have have owned 2 4Bs, 2 Bryston preamps, 3 7Bs, a BDA-1, and a BDP-1. And that confidence has extended to products it has distributed, but has not made - PMC speakers and a Torus C15.
When a relationship with a company can last far longer than many, if not most, marriages, you can call it a match made in heaven.
Dave