I used a 3020A for 32 years without any problems at all - in fact it still works perfectly. That said, NAD have been brought and sold a few times since then so it would be wrong to compare the modern products produced by a different company that happens to trade under the same brand name.
Also, one reason why NAD were so affordable 30 years ago was that they were one of the first 'British' Hifi manufacturers who sub-contracted production to low wage far east factories, although most others followed this trend afterwards. The result of that is it can be hard to compare and contrast, with often different brand names being produced in very similar places. It's a bit like drums - I used to play regularly, and had a certain brand loyalty (first to Premier, then to Sonor), but that was misplaced - nearly all the 'big names' in drums (with a few specialist and high end exceptions) come out of the same 2 or 3 factories in China regardless of whether they are a 'British', 'German' or Japanese brand. As a result issues of quality and reliability are surprisingly uniform, something that I doubt is very different in Hifi these days...