The other day I came to the conclusion that I use smiley faces enough to make the separate symbols/alphabet keyboards inefficient. The solution was actually pretty simple. First, knowing that iPhone users can program their own text shortcuts, I found this option in general settings under keyboard and then in shortcuts. There, I set a double h (hh) to autocorrect to a smiley face and double s (ss) to correct to a sad face. Now I don't need to switch keyboards except for exclamation points!
