I have to add my experience here. I have a 47 gallon tank with sump and bought more than 50 lbs of live rock to start with. Later on, I added 7 or 8 more pounds to fill a corner.
I ended up having too much live rock. My bimac Ollie grew bigger and started pushing out rocks into her sandy beach area, which she did use. She just shoved rocks out to make her den bigger and bigger. She also toppled the taller rocks. As I redo my tank now, I am removing rock because I realize I had too much. It was fine for a young octo but not for an adult. The sandy beach area is important for a bimc - it's an area for play and for catching crabs. I don't want to lose it the next time.