I do this as well...
Here's a few I have...
CONDITIONER 300 pts Good thru 02/10/08
CRUMBS 300 pts Good thru 02/08/08
ADOLESCENCE 300 pts Good thru 02/08/08
FESTIVE 300 pts Good thru 02/07/08
APPAREL worth 50 points good through 02/10/08.
Each word has an expiration date, so make sure to use it before it expires. Some words are not valid for very long. and yes, you are only allowed 5 tries per hour, so make sure the word is spelled correctly.