As long as it takes to finish. Usually I can get content updates out in ~3-4months of the previous release. Usually.
its alright if it takes time a rushed out update is never nice because perfection requires time to be made if it takes some time its okay i wish to play another awesome chapter/chapters of the story which was thought out with a calm mind rushing out updates is not good for the mind or body not saying it stresses out alot, and has high risk of burn out. i know that not because im a dev but because my life is always in a rush without a single time to take a breathe and take time for myself...