I believe that an SI was issued within TC not that long ago to stress the need to reiterate any previous restriction that the controller still wanted to apply when clearing an aircraft to a revised Flight Level or Altitude.
Despite being busy on frequency, if you want an aircraft to adhere to a previously issued restriction when you are clearing it to a new FL, you should reiterate the restriction. This ensures that you are in positive control of the aircraft and won't be caught out by crews interpreting instructions in differing ways.
Just a thought
