Apparently we're really not having much luck with Teespring this year. I have updated the above URL to reflect that I have had to recreate the campaign for a 3rd time!
The campaign was set to keep going and printing every 3 days until I end it, however it seems to not want to keep going past the 3 days...
I have set this new listing to last for 21 days (maximum they do), though I have also specified a custom end date of the 9th of Feb. (whether that'll work is anyones guess), however, this means any orders from this point will be held until the 6th of Feb. before they will go to print and be shipped. My apologise for this but it seemed like a better option rather than keep having to create URL's etc every 3 days (don't get me started on the 'relaunch campaign' button that they have, I presume, just for show).