In my experience sages are only available at certain (random?) times in the day,
I'm pretty sure its random. I have encountered sages at many different hour times.
When desperate to find a sage in a region I start with full hours then check to see if one is around, if not I spend an hour from my pool doing something (resting, gathering etc) then check again, continue until you find one (or not). Seems to be the best way to find a sage.
I am somewhat methodical and thorough, so I make sure I have full hours and at least 16 fatigue. Then rest one hour at a time until I find him