Depends on the circumstances. A 4-hour limit is OK on chargers intended to be used by people shopping or having a meal out, but it's absolutely unreasonable on a destination charger people might want to sit on all night. I am sick to the back teeth going out in the rain at one in the morning to re-start a charge on an AC charger near my friend's house, because it automatically cuts the charge after 4 hours. No actual overstay fee though! So I can leave the car plugged in and not charging as long as I like. It's nuts. (The chargers are mostly ICEd during the day, too.) Destination chargers absolutely should be available for all-night use. What the hell is the point of kicking people off them at two in the morning?
I think in a big car park the solution is to set say a 12-hour limit to avoid endless hogging, but to install more chargers if the ones there are are permanently busy and there is demand. Ideally nobody should be having to rush back to vacate what should really be an EV-equipped parking space before their business is concluded. Twelve hours should let anyone charge to full, and have an overnight sleep, and come back and unplug the car. Or spend as long as they like shopping or in a meeting or at the theatre, without worrying about the parking meter, as it were.
The issue is the small car parks, where more chargers can't be added without eating into the non-charging car park spaces. There, I think a four-hour limit in the daytime is reasonable, but (like in Penicuik) people really have to be allowed to use them overnight without unreasonable penalties or the charge being cut off arbitrarily.
