No one has jumped in, so here is what I tell people. You didn’t specify what harp, so some may not apply to you
Wires affect the sound of the entire harp, because they resonate with every other string on the harp. Many builders try to include at least 7 wire strings in the bass for this reason, if harp compass allows. Wires should be replaced every two years in regular usage. Maybe 3-4 years for casual usage. If they are not bright, or are corroded, they are long overdue. Ask a guitarist friend how much difference this makes.
Nylon and Fluorocarbon degrade gradually so that the changes are not usually noticed. In regular usage nylon not more than 2 years, fluorocarbon not more than 4 years. Somewhat longer for casual usage.
Gut usually breaks before it gets dead and ugly sounding, but not more than 3-4 years for regular usage.
Regular professional usage I recommend roughly half those times.
Fluorocarbon is for bright sound, and most of all for tuning stability, but that doesn’t mean it lasts forever. It still stretches and the polymer loses its cross-linking under the strain. It is still an expensive material, as is gut.
Most importantly, though, is that ALL new harps should be regulated at about the 2 year and 5 year point. Rarely does it sit on a builder’s floor long enough for any soundboard to belly completely under the strain.
Whether you can tell the difference or not, I can’t say. I’ve never restrung one over 5 years old that the customer failed to say “wow! I didn’t think it would make that much difference.”
12 years without a restring or a regulation is a looong time. Longer for some harps/builders than for others.
It is also important that the strings be put on correctly: non-slipping knots tied, wound on the pin the correct way, with the correct width of wraps giving correct string angle, and allowing for bridge pin height, tuning pin protrusion, regulation/buzzes in the lever assembly, etc.
Charles Nix
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