(* Where should this sit? *)
Section Timeless.
Definition except0 P := P || |>FF.
Definition timeless P := |>P |-- except0 P.
Definition timeless' (P : mpred) := forall (a a' : rmap),
predicates_hered.app_pred P a' -> age a a' ->
predicates_hered.app_pred P a.

Lemma except0_exp : forall {A} (x : A) P, except0 (EX x : A, P x) = EX x : A, except0 (P x).