Michael is definetely correct. When making leavened pancakes, a chemical reaction takes place that releases Co2 bubbles. It's these little bubbles that make the pancake rise. The chemical reaction only takes place until chemicals are "used up" so to speak.
That being said, a longer shelf life is obtained by using a double-acting baking powder. It has two sets of ingredients, one set that activates when liquid is added, and a wnd that doesn't begin its action until heat is applied. Even then, the best leavening takes place within minutes after the batter is made. Also, for the most tender pancakes, mix as little as possible, only until everything is wet. Small lumps in the batter dissapear as the panckes cook. Over mixing result in rubber pancakes.
For still lighter pancakes, replace 1/3 of the wheat flour with oat flour. It makes an incredibly light pancake. Unfortunately, it take some skill to flip these pancakes as they are very fragile and will break easily. You almost have to have two pans so as to flip from one to the other. But the regular home made recipe I use creates very tender, moist, and light pancakes without the addition of oat flour. I just find it fun to experiment with things. (see Goodweed's World Famous Pancakes).
And, even though pancakes are good after being frozen, they are best when hot off the griddle, and I mean right off the griddle. If they even sit for a few minutes, much of the moisture steams away, or if they are stacked, then those underneath can become soggy and squished down.
Anybody can make good pancakes. But great pancakes are and art.
Seeeeeeeya; Goodweed of the North