One can use 1/30 (not always practical), 1/60 (may be too long as well), or 1/120.
Indeed one could. You said "FL lights". Would your advice apply also to modern lamps with electronic ballasts?
Fluorescent lamps using high-frequency electronic ballasts do not produce visible light flicker, since above about 5 kHz, the excited electron state half-life is longer than a half cycle , and light production becomes continuous. Operating frequencies of electronic ballasts are selected to avoid interference with infrared remote controls. Poor quality (or failing) electronic ballasts may have insufficient reservoir capacitance or have poor regulation, thereby producing considerable 100/120 Hz modulation of the light.