Time works differently in Faeland. Days in Faeland are like years in the human realm, like “dog years” – so a few minutes spent in Faeland will be hours in the human realm.
Jax and Birch are guards who are patrolling the borders of Faeland. Jax is a dragonfly faerie, who lives a very short life by fae terms, 24 years – so 24 hours in the human realm. He’s currently 22 fae years old, so when he goes to human land he only has 2 hours left to live – which he knows. He does it as a sacrifice for his people? Maybe I’ll give him more time. Depends on what he has to do – but it is a ticking clock. Find the breach and shut it as soon as possible. Kim doesn’t want the breach closed while Tiffany is on the other side.
So when the group of humans is in Faeland, they are actually gone from the human realm for a few hours. And Tiffany and John Michael (if he’s there) stay in the Faeland for much longer.
Birch, btw, is a tree faerie, sort of like an Ent, and has a long life but grows slowly. She can’t go to the human realm because she’d lose her ability to move about. Both faeries look human enough that the human group doesn’t freak out too much when they see them (and think that they are just a product of their collective acid trip – but one of them has to realize that group tripping does not mean seeing the same hallucinations.)