All of those clean up crew packages posted on the main sites seem too big to me too. I was looking at various packages for my 40 gallon tank and they were suggesting 20 of this and 20 of that. I decided to just add them slowly and see how they did.
I added 6 hermits (3 scarlet, 3 blue-leg), 2 margarita snails, 1 turbo, and 1 emerald crab. They have been in the tank for around 3 months and I have seen no need to add anything else. They are doing a great job of keeping things cleaned up so I would imagine that 20-40 crabs, 40-50 snails, and whatever else was included in those packages would starve.