Yes, an advantage of Pressbooks is that it’s quite simple to create and publish digital work, and then keep adjusting and updating it over time. So long as you maintain an active subscriber account, you have access to add, edit, and adjust your content. If your work is openly licensed, then Pressbooks will continue making the book available on its server even if you decide to end the subscription at some point. However, if you wanted to make further updates after that point, you would need to reactivate your subscription in order to restore editor access to the book.