You can use it as many times as you want, just change you IP. I've bought a couple of mouse pads for friends, and now I'm waiting for a 'dog tag' which I will use as 'person tag'.
Yeah, it is very cool. Now with my new connection I am really struggling to get a new IP to use it again. It is quite difficult to choose what picture to print. I want one mouse pad or tag for each rock band I love.