Bread – Uses for Old bread dough

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.

Salt has an effect on the enzymes in flour, as well as how the water affects gluten development and yeast activity. Generally when salt is added later in the mixing process, it is to allow more time for enzymatic processes to happen before the salt inhibits them. (Alternately, you can add salt at the very beginning with all the other ingredients as long as it doesn't come in contact with fresh yeast.)

Kneading dough without salt can help the gluten to develop faster, and give you a very smooth, extensible dough. The problem is that then you have to knead dry salt into a developed dough, which can be pretty hard to do.

Letting the dough sit without salt (called an autolyse) allows for enzymes to do most of the gluten development work before you start actually kneading it, letting it form a developed dough very quickly. The advantage of this is that the dough is not yet fully developed when you add the salt, so it's a lot easier to get it incorporated.