I'm out her in Arizona and they tell me to water for 90 minutes and I have 4 zones with 2 gallon drips. The 1 gallon drips clog up to much. So I water all my plants for 30 minutes every third day and the trees are on a 1-10 gallon drip. Now when the winter comes I can tune it to once a week for 30 minutes. If you have good wells for your trees and they don't overflow then what's wrong with a 30 minute drip?
Richard