So I have a beutiful rice 20th century silk set. And I am buying a rice symphatetic silk set I am just slightly worried that the silks will not last that long since they are 6 momme. Is this a problem or am I just worrying for nothing?

It depends on how many shows that you do! The corners are what wear out first on silks that get tied into hard knots. Washing your hands will help, but it's mostly the twisting and pulling that causes the wear. I used sympathetic silks, which uses square knots, but, they were never pulled extremely tight. In school assembly work (average 13 shows per week, I could get sometimes two seasons from a set. I always carried "back ups".

With 20th C, it's a square knot, also, I averaged two seasons.

In later years, I found some beautiful polyester "silks"(?) that looked and, worked fine for sympathetic silks. I tried them as the two "end" silks in 20C, with a Rice "rainbow" in the middle. It worked fine.

Almost any can, pan, tube, box, or "red velvet bag on a stick, will wear out, depending on use and care.

If you do mentalism, you can get by on 3x5 index cards and a pencil.
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I used Rice Silks for years. I have 72" Rice Dragons 40 years old!

Thanck you Dick! Your comment makes a lot of sense and I am no longer as worried about the durability of the silks.