Ideally the firmware of your printer should be configured so that 100 is typical.

I print at 100 unless I'm doing 60mm/s prints (typically I do 35mm/s), in which I usually jack up my temps +10C and my flow to 110.

My last tip is: The consequences of under extruding are less detrimental than for over-extruding. However, at really low speeds (<15mm/s) you really do have to be concerned about heat soaking the filament and causing a nasty jam.