1 month should be fine. I would try to see if there is solid roots growing first. 1 month in you should have plenty. Use a diluted dose at first and increase its potency over time.
You can use it full strength the day it's cut off the plant. You are one of the few using neem right, it is a preventative. Spray need and a wetting agent once a week from clone to week 4 of flower and you will never have mites or many others pests.