After chicks hatch, how long should nest remain up?

If it’s in a tree, leave it alone... if you go and take the nest down you’re fully invading that poor birds space and it’s home, people don’t come into your house and remove your bed after you have slept in it or made some chicks of your own in your bed. The bird will remove the nest by itself then will create another one when it’s necessary. Same as you sell your bed then buy another one.