You can use the quick recipient list to insert short bits of commonly used
text. Just make an address book entry containing the text as if it were
the nickname and check the option to put it on the recipient list. When
you want to insert the text right-click and choose "insert recipient"
then pick the text you want. (I do this with some addresses that I find
myself commonly telling people about.) That won't work for longer items
though. If you commonly insert larger blocks of text, you might want to
look at some of the utilities available for assigning text to keyboard
shortcuts. Some of those work quite well.