There is always something to learn. For example, you could memorize tap and drill sizes, motor speeds, research materials, study robot photos from previous years, find out what products are available, study the hundreds of white papers and presentations written by veterans, learn CAD, memorize formulas, etc. Anything that could save you even the smallest amount of time during build season is beneficial. I have been compiling calculators, presentations, robot photos, build notebooks, and reference sheets into one folder for my personal and team's use. You might find it useful.
FRC Resources folder