What ever BW says has to be gospile! Seriously they do know alot about bows and such but seems like every thing trad comes back to what BW says!
IMHO when you start seeing "fuss" on your string it's breaking down. period. All the waxing in the world isn't going to make it come back together and be stronger. How much longer you can go, well that's the million dollar question. How much have you twisted the string to make it the right length? How much have you shot it? If you have twisted and twisted to make it the right brace height, VS actual length then you have done two things. You've made it worthless and you've made it weak. When you twist a string too much it never twists past the loop section regardles endless or flemish. You've made a weak point in the string at the end of the twists! I'm also of the opinion string wax just adds weight and possibly adds to the weakness of a string. I don't add grease where it can catch dust and make the grease a sandpaper,same with string wax.
I guess after making my own strings for years now I just can't imagine anyone not making their own. There are instructions on here for making jigs and strings that anyone can follow.It was one of the first things I learned to do, then fletching, then making arrows and finally my own bows. If you don't have the time then just buy a new string cause theirs several great string makers as sponsors here. Strings are one of the cheapest things in trad so just replace them if like someone said your gut tells you too.