Bread – Why does this recipe call for so much yeast

First off, how do you store your yeast? Storing yeast in the fridge helps it to last longer; I've had some yeast in my fridge for a year that is still going strong.

As your yeast begins to become ineffective, I would personally get new yeast. Once yeast looses its power, you're simply not going to get the same effect out of it.

In both cases, you don't add the recipe's amount of water to the proofed yeast. If your recipe says e.g. 500 g flour, 300 g water and 10 g fresh yeast, you measure these 300 ml water, then pour some of the 300 ml over 10 g of pressed yeast to proof it, adding a teaspoon of sugar if you want it quicker. After that, you mix flour, proofed yeast and the remaining water together (for simplicity, I left out salt and possible other ingredients).

You do it exactly the same way with dry yeast, only you have to use the correct substitute ratio, which is 3:1. So you measure 300 ml of water and (1/3)*10 g = 3.3 g of dry yeast. Then you pour some of the 300 g of water over the dry yeast, and after it has bloomed, you mix flour, sponge and the remaining water. The bread hydration stays correct, and the fermentation time/amount is equivalent to the fresh yeast case.