Yeah you can do that but i think it also uses HP? each trip in costs X hp each time.
Generally not doable at the start but exploitable at the end of the game where it no longer even matters.
I started a bit of an experiment with 2 sets, 1 set of smol tiddy Inu's and another with nig tiddy to see how much milk they produced and if smaller was better to trigger the ability more often... but the data was scrambled and i ended up adding too many girls to the mix and got too much milk to count too often
I think it doesn't matter in the end, smaller trigger more often but for a smaller amount, larger trigger less often for a larger amount.