(25 Apr 2014, 4:16 pm)Dan wrote The date of expiry is apparently 04/05/14, but I can find no evidence of whether this is how long you have to enter the code or use the ticket by.

Found this on the website Dan - http://www.arrivabus.co.uk/catch-the-bus-week-terms/

So you'd just need to "purchase" the ticket by the 4th, and can actually store it until the end of the year. Definitely worth keeping one just incase.