Mark the token as expired, because invalid gives no clue of what to do next.

config/locales/en.yml

@@ -3,6 +3,7 @@
 en:
   errors:
     messages:
+      expired: "has expired, please request a new one"
       not_found: "not found"
       already_confirmed: "was already confirmed, please try signing in"
       not_locked: "was not locked"

lib/devise/models/recoverable.rb

@@ -116,7 +116,7 @@ module Devise
             if recoverable.reset_password_period_valid?
               recoverable.reset_password!(attributes[:password], attributes[:password_confirmation]) 
             else
-              recoverable.errors.add(:reset_password_token, :invalid)
+              recoverable.errors.add(:reset_password_token, :expired)
             end
           end
           recoverable

test/models/recoverable_test.rb

@@ -192,7 +192,7 @@ class RecoverableTest < ActiveSupport::TestCase
 
       assert user.valid_password?(old_password)
       assert_not user.valid_password?('new_password')
-      assert_equal "is invalid", reset_password_user.errors[:reset_password_token].join
+      assert_equal "has expired, please request a new one", reset_password_user.errors[:reset_password_token].join
     end
   end