Proof using.
intros x s J P rl.
change (P (Cons x s) /\ (J (Cons x s) \/ release J P (tl (Cons x s)))).
destruct rl; intuition.
Qed.
(* inf_often and continuously facts *)

Lemma inf_often_invar :
forall (x: T) (s: infseq T) P, inf_often P (Cons x s) -> inf_often P s.