I purchased AP passed in February to use in May. I emailed Universal:
Hello,
Thank you for contacting Universal Orlando Resort!
There is no time limit to activate your pass. If you would like to wait until the turn of the year, you won’t have any issues using your pass. Please keep in mind, once you activate the pass, it will only be valid for the length of time it was purchased for (12 months is the usual term). If you have any other questions about your pass, please contact us at the number below!
Should you be in need of additional assistance, please contact a representative via phone at 407.224.7840. Our office hours are Monday through Sunday 7:30 am to 7:00 pm EST.