Sustained harvest to me means fully established plants that will reliably produce every year. So with that in mind, Bananas
should be there 3 years after going in the ground, Plantains would be the same, yucca should be in the two to three year period as well.
Fruit
trees are seven years when grown from seed, if you plant a nursery raised tree expect it to be two full years before you get much fruit. The first year and sometimes even the second year for these trees, you want more
root growth than fruit so the tree is very well established and able to support
a larger crop of fruit. We pick off any fruit the first year then prune for shape the second winter so there will be more root growth and held fruit set the third year of being in the ground.
We also try to prep the soil a year before we intend to plant fruit trees. Next year I am hoping to get some banana trees and plant them in a grouping for better fruit set.