Re: Old strings and tone
I rebuilt an amp for a guy a while back, he is a respected pro player (country/jazz kinda stylings) and he told me he only changes strings once a year or so. When he came to get his amp, he bought one of his guitars and played, and he sounded great. So it seems to work for him anyway.
A long time ago when i was teaching, one of my students turned up with a broken (steel) string. I had some spares, and fitted a new string for him. The next week i asked him how it was having the full set of six strings again, and he said something like " I don't like the new one, it's too twangy".
It seems to me that better quality guitars and gear tend to show up the strings' condition more .... good acoustics in particular seem to reach a point where they suddenly sound very average and tuning becomes a nightmare. If I'm not gigging, my main concern is to change the strings well before they reach the point where they can be damaging the frets, but my guitars usually demand fresh strings long before then, the notes stop singing and become dull 'plonk' sounds instead.