Conventional wisdom says that composting worms like to stay in the top 6 inches of the bin. Experience with flow through bins tells us that they will go deeper if there is enough airflow in the bin. Unless you can provide enough airflow deep into the bin, I would not go more than 10 inches deep. Even at 10 inches you may find that the organic matter near the bottom of the bin is not getting eaten.

If you want to put off harvesting, go with a deeper bin, but keep the bedding depth at about 6 inches until it is well processed. Then you can add more bedding on top of that. You will need to add bedding just to keep the depth at 6 inches. Damp VC can be pretty heavy, so be sure you can handle the bin when it gets full.

Shallower bins are definitely easier to manage.