I went in to my local dealer and to buy my 2nd 4mix. I have a BR600 that I really like so I thought I would try a FS90 trimmer(so far so good). Anyway, I asked what was the deal with the early BRs as I learned from this forum. He said that the early units did have some issues with soft exhaust valves, but that mine being a newer model would be fine. Then for the good part, he said not to worry about it however, because even if I did have a problem in this area with the engine, Stihl would take care of it even outside the warranty period. Don't know if this would be the case, but it sounds like Stihl is manning up to the problem. Made me feel better about the company and product. Seemed to be sincere.