If I understand your question, the length of the tie is a result of a number of factors, not a specific length. You don't want to be too close to the wall because when the slack in your chain/rode is stretched in a wind, you hit the rocks. Everyone may have a variation on method, but what I do first, is get a firm set on the anchor based on depth--I never set the anchor with less than 3:1. and other conditions such as anchor type and bottom conditions, depth at flood and ebb, adjacent rocks, other boats etc...Once the anchor is set I run the stern tie ashore and back to the boat and cleat it off. Then I pull the boat in. Neither stern tie or chain/rode should be completely taut nor have a lot of slack. Many anchorages have stern tie rings driven into the rocks. This makes what Ghost said easy--you don't have to go ashore to release the tie. You may find yourself messing with it for a while and you should definitely check it as the tide changes or if a strong wind comes up.
I think a 600' spool is common for the general area. I don't think you need that much for McDonald Island rings though. Not a lot of anchoring there anyways.