I just don't get how staying put for a week is a "fairly safe" option when giant ape creatures keep attacking.
Scotty's comment about "a phaser can only drain so fast" tells us that it is a very slow process, so waiting until the last minute doesn't work. Again, the creatures aren't happy with them being in the area. Without provocation, they speared Latimer. Once Spock went on the offensive, the creatures were pissed. They were smashing the shuttle with boulders. Spock scared them off, but they came back. Once the batteries burned out, there would be nothing to stop them from damaging the shuttle to the point where it couldn't lift off at all. I don't understand why you think they could hold out for six days under these circumstances. Not a chance. And then consider Kelowitz's report:
KELOWITZ: Ensign O'Neal got a spear through the body before we even knew they were around. Lieutenant lmmamura has a dislocated shoulder and severe lacerations, but he'll make it all right. Captain, the creatures are all over the place. If the Galileo is down on that planet…
The clear message is that the shuttle crew cannot survive for long down there. Drained phasers = no weapons. Possibly little or no food or water. Even if you could hold off the creatures with stones or clubs, why would you WANT to delay departure in this situation? Wouldn't you want to leave the planet ASAP? The sooner you leave, the better the chance of the survival of everyone left. If Spock dilly dallied and let the Enterprise fly off, how many of the crew would be left to pick up on the return trip? They already lost two in the first few hours. That would also make him a pretty crappy commander. The landing party is in jeopardy. If you were in this situation, would you be okay with waiting around a week for the Enterprise to come back and keep searching?