I would wait until the 15th of this month to see what the next Mousesavers newsletter has to say about special prices from Ticketmania. I would think there is a pretty good chance new specials may come along similiar to those they have that expire this month. This is only a hunch, however. No reason not to wait. Regardless of where you buy your tickets you'll have them in plenty of time if you wait until after the 15th.
Thanks everyone! We actually bought the ten-day no expiry tickets because we will go again another year but my mom is coming and doesn't want to spend that much. I'll tell her to check out the link above!