YES! Seal the Back. Seal it as soon as you finish bringing it down to one ring.
It might be a good idea to seal it as you go by sealing small areas as you finish them.
I almost always stop one ring shy of where I want the back to be. Seal the stave up tight and let it dry.
Once it is dry the last ring is taken off along with the sealer. That is just the way I do it.
Unless you have a hot box, or something that will work as one, there is not much chance this stave will be dry in three or four weeks if it is fresh cut.
David