It’s one year cooldown after joining a family share. I.e. if you leave half a year after joining, you have to wait another half a year to join another family share.
Adults can leave a family at any time, however, they will need to wait 1 year from when they joined the previous family to create or join a new family.
Good idea to write a function, I’ll do that right now. Over the last few weeks I’ve been regularly doing the Ctrl+Z, bg, disown, which does get old pretty quickly. At least I now remember the terms and don’t have to search for them each time I need it :D