Here's the reply I got from HTC.
So basically unless your carrier has a different plan(insurance or whatnot), the battery is only warrantied for the first 12 months.
Dear *removed*,
Thank you for contacting the HTC Technical Support Center in regards to the HTC One enquiry.
We are really glad to hear you are interested on purchasing our last release the HTC One. The warranty that covers your device is for twelve months period in which any manufacture or develop issue can be solved under it. That will be the coverage that HTC as the manufacturer of the device gives. However Verizon may have different policies which can not be explained from our hand. Cameron, we encourage you to reach them and double check with them. The battery inconveniences are mostly covered if after the analysis performed on or RMA Center is discovered that it is a fault on the device it self. That will cover your warranty for certain situations.
To verify the HTC warranty that covers our devices you can visit us at https://support.htc.com/alerts_downloads/en/Warranty_Policy and look for it. If you require further assistance in the near future please contact us through Contact Us or call us at +1-866-449-8358 from 8AM to 1AM, 7 days a week.
Have a nice day,
Sincerely,
Julian
HTC
Thank you for contacting the HTC Technical Support Center in regards to the HTC One enquiry.
We are really glad to hear you are interested on purchasing our last release the HTC One. The warranty that covers your device is for twelve months period in which any manufacture or develop issue can be solved under it. That will be the coverage that HTC as the manufacturer of the device gives. However Verizon may have different policies which can not be explained from our hand. Cameron, we encourage you to reach them and double check with them. The battery inconveniences are mostly covered if after the analysis performed on or RMA Center is discovered that it is a fault on the device it self. That will cover your warranty for certain situations.
To verify the HTC warranty that covers our devices you can visit us at https://support.htc.com/alerts_downloads/en/Warranty_Policy and look for it. If you require further assistance in the near future please contact us through Contact Us or call us at +1-866-449-8358 from 8AM to 1AM, 7 days a week.
Have a nice day,
Sincerely,
Julian
HTC
So basically unless your carrier has a different plan(insurance or whatnot), the battery is only warrantied for the first 12 months.