Hi,
Both of these models are covered under Cisco standard 1-year replacement warranty as per the datasheets
http://www.cisco.com/c/en/us/products/collateral/collaboration-endpoints/unified-ip-phone-8800-series/datasheet-c78-731667.html
http://www.cisco.com/c/en/us/products/collateral/collaboration-endpoints/unified-ip-phone-7800-series/data-sheet-c78-729488.pdf
HTH
Manish