If you don't use keyboard shortcuts on your iOS devices then it is something you should consider. I have a couple I have on my iPhone which I use all the time, plus many more on my iPad. They do save a lot of time, I wish I could use text expander more on the devices, but this can't happen due to the restrictions set by Apple. I find them very handy when filling out address and email information. The keyboard is small enough on the phone, and anything that makes life a bit easier has to be a good thing.
To get to the shortcuts, go to Settings -> General -> Keyboard. Go to the bottom and you will see Shortcuts. There is a button there saying Add New Shortcut.
From here in the top box that says Phrase you add you long string, i.e your email address, or the first line of your address. Then in the second line you name your shortcut. Once you click save from there once you type your shortcut it will expand to the full phrase.
Below you can see the few I have on my iPhone, 20HA - My home address for filling it in, gcem - my email address which you are always entering logging into sites etc, hsas - The little message I have which lets the wife know I have got to work safely when I am riding my bike, simple four characters and then press send.
I am always interested in feedback so please feel free to add any comments, or you can mail me here. If you would like to submit a quick tip with full credit and links back to your site then also feel free to contact me.