How long is one covered when purchasing Apple Care+?

Also depends on if monthly payments are available which have no set expiration dates. Regular pay up front plans are 2 years for iPhones and iPads, and 3 years for computers. You can buy within 60 days of device purchase and the Applecare will end 2 or 3 years from date of device purchase.

It depends on the product you’re protecting and country you are in

AppleCare Products - Apple

You’ll need to see what options you have and you may be able to pay monthly and extend your coverage

For a Mac, you can also choose to pay annually for AppleCare+, and it can run for longer than 3 years if you continue to renew it.