When a federal trademark registration is up for a renewal for an array of goods or services, there either must be continued use or excusable non-use for every good or service listed in the trademark recitation. 

Frequently, some trademark firms simply have the client sign off on the original listing of goods/services and never check to see that all of them are still in use.  If the trademark is challenged and the listing is overreaching then you have fraud on the USPTO, unclean hands, and the invalidation of the entire trademark registration.

Say you registered the ABC trademark for tea and coffee bags.  If you stop selling tea with the trademark you redact that at the time of renewal.  If you resume branding tea by the time of the next renewal you cannot “add” tea back into the trademark registration.  Once redacted, it is gone forever.  To maintain trademark rights there must be continued use. In theory you would need to file a new trademark application listing tea under the brand. 

That being said, trademark recitations are not interpreted as literally as patent claims.  Say a third party decided to sell tea with the ABC trademark.  Even though tea bags are no longer expressly enumerated in your recitation, you have coffee bags.  A reasonable consumer would believe that coffee bags with the ABC logo are controlled by the same source as tea bags with the ABC logo.  

Therefore, even though the ABC trademark registration enumerates less items, it would still protect against such infringement.