@ElectricBlueBee
The point of having a supply of mated queens is thus:
If you have to split a colony as part of swarm management, then the part without a queen will effectively cease producing honey. The time to get back into production is the time for the a new queen to emerge. Nominally twelve days assuming that you split the colony two days before the cell was sealed. Two to three days to mature and a further couple of weeks to become mated and begin laying (or more). Three weeks for the eggs to become workers and a further three weeks for those workers to become foragers.
By replacing that cell with a mated queen introduction, after having made them hopelessly queenless, then the break in brood rearing is minimal rather than a month, in which time the colony will be reducing and so it's rearing capacity diminishing, albeit slowly.
So the secret of production is to have big colonies with plenty of room (supers) and fresh laying queens that have lots of queen substance to hold the colony together and not allow them to swarm. The other point of course is that these are queens raised from queens with the traits that you want and not swarmy queens or just random outcomes.
The buffer mechanism is mating mini nucs to establish mated queens for short term use to fill a shortfall in queens and to replace older failing queens, nucs to grow backup colonies that can be used for colony increase , sale or bolstering colonies that need frames of emerging brood to maintain the production work force.
It all seems to be a bit of a catch 22 question at times trying to get the balance right as the seasons and the world flash by before you, but that's the theory as I understand it.
The idea is to keep your honey factories fully manned (girled) and motivated, if you can.
Easier said than done at times. 
with PH.
