The old rule I was told when starting out was to make a culture a week per frog, then back off from that as needed. Always at least making 1-2 extra for backups. Unless your conditions are exactly the same (temp, light, humidity, contents of medium, and ff strain) you can not depend on always getting the same results.
Example, I get a much better production in the fall/winter than I do in summer. The temps are only different by a couple degrees, and it is less humid in the summer. I have not yet tested to see if I get less production or if it just takes em a little longer.
As for feeding it depends on how many frogs like Arklier said, and the size of the tank. 3 frogs in a 20 gal will need less than 3 frogs in a 100 gal, as the food is easier to find.