I emailed PhotoPass customer service to check for sure how long the codes are good after you purchase them and got a VERY vague response. Here it is:
Thank you for your recent visit to DisneyPhotoPass.com. The pre-purchase offer is made available through the marketing department of Disney Destinations. In order to receive this prepurchaseoffer, the guest must meet the following guidelines: -Have an upcoming reservation in a Walt Disney World Hotel -Have their email address on file in the marketing database -Have opted in to receive email from the Walt Disney World company If you meet these requirements, you can expect to see this email about 10 days prior to your arrival. Once you have received this email, you are within a safe time frame in which to make your prepurchase without worry that your promotion code/s will expire. If you do not receive this offer, it could be because your email addressis not on file and/or permission was not granted to send marketing messages to you. Also, if you booked through a travel agent, we may nothave your email address in our database. The pre-arrival offer is meantfor guests who purchase before their trip. If you have lost your offer, we regret that we are not able to replace or extend this invitation as this offer is not sent out by Disney Photo Imaging. Sincerely, DeborahDisney Photo Imaging Guest Support Team
Don't think I'll tell them that people like us pass the code around even when we're not "invited".