You can change the default expiration. See the initializer at

https://github.com/nsarno/knock/blob/master/lib/generators/templates/knock.rb

  ## Expiration claim
  ## ----------------
  ##
  ## How long before a token is expired. If nil is provided, token will
  ## last forever.
  ##
  ## Default:
  # config.token_lifetime = 1.day

You should be able to set the token_lifetime to nil to make the token never expire if that is a requirement as well.

config.token_lifetime = nil