5* Heroes
Depend on RNG, it could take you 5 years to get Joon ( see notes ).
If you are leveling multiple 4* troops and multiple 5* Heroes, you many need the food to level these instead of running Legendary Training.
My personal situation
With my play style, I am running 2x RT11, 1x ( RT11 or RT19 ) and 1x RT20 and this usually consumes the same amount of recruits I farm for no increase in training queue.
If I decided to change from Legendary ( RT20 ) -50 recruits per day - to Guaranteed rare ( RT12 ) - 22.5 recruits per day - for food storage this would just add more recruits to my 3x RT11 since I cannot get enough Rugged Clothing ( and recruits ) to increase my use of Extra fast training ( RT19 ).
Switching to Guaranteed rare ( RT12 ) would let me have a larger food buffer, but I have already Off color, 1 day, power leveled both Proteus and Wilbur without making a significant dent in my food buffer. So a larger buffer should not be helpful with my current spending habits.
Since I am running Legendary ( RT20 ), I am also keeping 2 of each 4*/ 5* hero since we do not know how the Hero Academy will work.