NORMAL DOORS: Doors in a dungeon are usually closed, and are often stuck or locked. A lock must usually be picked by a thief. An unlocked door must be forced open to pass through it. To force open a door, roll Id6; a result of 1 or 2 (on Id6) means that the door is forced open. The roll should be adjusted by a character’s Strength score adjustment. The number needed to open a door can never be less than 1 nor greater than 1-5.
Once a door is opened, it will usually swing shut when released unless it is spiked or wedged open. Doors will usually open automatically for monsters, unless the door is held, spiked, or closed with magical spells.1981 D&D Basic Rulebook, page B21
I am a big believer in the Open Doors check. Not only does it help establish the fact that dungeon doors are hard to open and that characters become strangers in a strange land by entering the dungeon, it is part of setting up an encounter with whoever or whatever might be behind that door. If the initial attempt to open the door is unsuccessful, surprising anything behind it would be almost impossible.
However, I am NOT a big believer in repeated failures while trying to open doors. While it might be “realistic” in a sense to require repeated attempts if no one can manage to get the door open, it generally ends up being an unfun exercise in groans. So I have decided to generally only require a single, initial, Open Doors check.
If the attempt is successful, the door is opened and surprise may be possible. If the attempt fails, I will rule that the door is eventually forced open, assuming that it is openable. I will rule on the time required if it matters, probably using the how badly the roll failed as a guide. This should cut down on the repeated rolling.
Of course, there may be circumstances where rolling until the door is opened make sense, and in those cases we will do whatever we need to do to play it out. But, in general exploration with typical doors and unexceptional circumstances, one roll to see if the door can be forced quickly on the first try will be all that we dice for.