Apple has updated the way AppleCare+ works in the US for its Mac models, with an updated support document to back it up too. AppleCare+ in the US can now be extended for more than three years in the US only for Macs, for example if you had purchased a three year plan for AppleCare+ it would expire after that period, but now you can choose for the plan to renew on its own annually indefinitely, at least until it is canceled.
This system has already been put in place for the iPhone, in the US and the UK you have the option to pay for AppleCare+ coverage on a month by month basis and it too can run indefinitely, at least until it is canceled.
“AppleCare+ for Mac is an insurance plan that provides up to three years of expert technical support and additional hardware coverage from Apple, including up to two incidents of accidental damage protection every 12 months, each subject to an excess fee of $99 for screen damage or external enclosure damage, or $299 for other damage.3In addition, you’ll get 24/7 priority access to Apple experts by chat or phone. Coverage begins on your AppleCare+ purchase date.”
For the time being, AppleCare+ coverage beyond three years is only available in the US.