Being considerate goes both ways. It would be inconsiderate to leave your car plugged in hogging a spot even though it is done charging.
However, it is worth mentioning one possible reason a person might want to leave their car plugged in: Pre-conditioning. Lets say it is super cold or super hot outside. A person might want to be able to precondition using power from the EVSE. And I could see doing this for 15 minutes or so after your car is done charging. I can't see letting it sit there for hours on end with no activity, though.
However, honestly, if there are other people waiting to use the EVSE, I say your time is up once your car is charged. If you want to pre-condition then do it while the car is still charging.
I would think that the luxury of pre-conditioning should be reserved for your own charging station at home and not for public usage. I would apply the same rules/etiquette that are used at gas stations, (well, should be used, there are some ignorant folks around.) If the station is pretty busy, stay by your vehicle while refueling so that when it is finished you can move it so someone else can begin the process, meaning, don't go in to the store and get your coffee or use the facilities while you are refueling.
Who here would ever remove the nozzle from a car at a gas station that was not their vehicle? I would hope no one would do this. Shouldn't the same logic be applied to EV charging? As a responsible driver you should know how much gas your car holds and so too you should know how long a charge takes for your EV and therefore you should be available to move your vehicle within 5-10 minutes after the charge is complete. Of course I am dreaming that others would be so considerate as to be paying attention to anyone beside themselves and that is becoming more and more rare in our country, I wonder why that is.