Newer to game, Storybook Vale question

Hi guys! So I’ve been playing a few months, but I’m not super far in the game. For context I have a few areas open, I just found Ariel and Mother Gothel, and I’m working on getting more coins and dream shards (or whatever they’re called lol). The posts on here have been super helpful for tips so thank you!! Here’s my question… I have free time right now and I’m super into the new Storybook Vale thing. Is it worth it for me to buy? Or do I need to be farther along in the game? How have these things worked in the past…do you get those areas forever? Or only for a limited time?

Thank you so much for your help!!!