Floss is often / typically Nylon, which will take decades. If you accidentally wound up with PTFE floss (which is apparently a thing) I'd expect millennia unless it's in direct sun.
Tampons should biodegrade at home, but I'm willing to bet there are large swaths of the US where composting anything with human fluids is illegal.
In any case, hat-tip for empiricism! Very pro composting, wish it was safer, smaller, and easier to do at home.