In my opinion 10 mins is a bare minimum to watch a ledge, especially one you’ve never fished before.
You need long enough to see the pattern of swells coming through and as others said, how they react to coming over a ledge.
My starting point is a question, is the ledge wet? If so, wait long enough to see why!
The swell that came over the ledge in the footage seemed significant and the wet ledge told me it wasn’t the first wave to go over it.
Also remember that as the tide changes, so will the amount of water coming over a ledge even if the swell stays the same. Which it might not, swell can easily change bigger, smaller or a different direction during a fishing session.
You need to be aware of how the ocean is behaving and possibly changing at all times, especially on low ledges.
I hope everyone stays safe and gets to go home to their families.
cheers,
stu.