How long does a trademark registration last?
For a trademark registration to remain valid, an Affidavit of Use ("Section 8 Affidavit") must be filed: (1) between the fifth and sixth year following registration, and (2) within the year before the end of every ten-year period after the date of registration. The registrant may file the affidavit within a grace period of six months after the end of the sixth or tenth year, with payment of an additional fee.
The registrant must also file a §9 renewal application within the year before the expiration date of a registration, or within a grace period of six months after the expiration date, with payment of an additional fee.
Assuming that an affidavit of use is timely filed, registrations granted PRIOR to November 16, 1989 have a 20-year term, and registrations granted on or after November 16, 1989 have a 10-year term.
This is also true for the renewal periods; renewals granted PRIOR to November 16, 1989 have a 20-year term, and renewals granted on or after November 16, 1989 have a 10-year term.
More info can be found here.
http://www.uspto.gov/