For light wind, I typically use 50 foot or shorter. Lightest of all wind is indoors, where I have sets from 7' to 15'.
Short lines mean a smaller window, meaning less legwork to work the wind window, which is often necessary on UL/SUL conditions. They are also lighter.
Nothing prevents flying on long lines if you want if the conditions let you.
And as for specific lengths like 85' or 100', those really only matter with groups. For dual line teams both 85' and 135' are common, so they are good to keep on hand. I flew today with two novices that happened to be in the park; their Prism Jazz kites came with 85', so I pulled out the same length from my bag as I joined and talked with them. My Kymera flew at a different pace but overall we could fly together. Having common lengths is convenient.