its not really about the distance you can cast but more about fishing in the rite conditions. Beaches are best hit on a dying sea. look for dark patches in and behind the surf, these are holes and gullies where the cod prefer to feed.
Its no good casting 120 yards onto a sandbar if the fish are feeding 50 yards out in a gully. Another thing to do is take a walk along the beach on a large low tide and look for holes and gullies which you can cast into at high water. Here is when a larger cast will com into play. Hope this helps. roppa