manufactured front door finish needs help
We installed double front doors we bought from the builder supply 5 years ago. They face east, are recessed, and some areas get early morning sun every day for 3 or 4 hours. The varnish or laquer finish is looking dry and the stain is fading here and there. They have leaded glass sections on the upper half and are constructed of several different planks of stained wood. Some have faded more than others.
I would like to improve their appearance and protect them, but I do not want to have to refinish them.
What can I rub into the surface to protect the wood?