The combos that I like best are mung and millet, red lentils and brown rice, adzuki and red rice, mung and buckwheat, teff and French green lentils and many others. The larger legumes don’t seem to work as well as the smaller ones and almost any grain will do. It is fun to experiment with this. I love how they get sour and so tasty and hold up better than tortillas.
I like to put a sheet of waxed paper between them and freeze them. (They last up to 6 months) They will also last about 3 weeks in the refrigerator. If you don’t use all the batter, it will last about 2 weeks in the refrigerator. When you go to use it, you might have to stir it and add more liquid.
Any leftover batter will last for a couple of weeks in the refrigerator.
I also discovered that if you leave the batter on the counter top too long that it can get quite funky looking but if you can peel off the gross top layer, you can still use the batter underneath. However, my rule of thumb for this ferment and others is "if it smells funky, looks funky and tastes funky" throw it out.