That doesn't tell you how long you can stay parked. How useful is it to know that you're currently allowed to park, without also telling you it's going to chang

That doesn't tell you how long you can stay parked. How useful is it to know that you're currently allowed to park, without also telling you it's going to change to "No Parking" as soon as you've left your vehicle? EDIT: If you could do a countdown timer to the next state, though, that'd be useful.