Apple has extended the time to renew AppleCare+ coverage from 30 to 45 days after it expires. This update applies to customers in Australia, Canada, the U.S., and several European countries.
According to the AppleCare+ document, coverage can be extended for 24 or 36 months, or on a monthly or yearly basis until canceled.
You can check your AppleCare+ expiration by going to Settings > General > About > Coverage on your iPhone or iPad, or System Settings > General > About on your Mac.