Help w interior shelf with beeswax and mineral oil being used outside

I built a small shelf for a friend that was intended to be for inside since I used beeswax and mineral oil to finish it. He actually is using it in a covered potch area but after a year or so, it's not holding up well, which isn't too much of a surprise. Is there an easy way to improve the weather resistance for this such as applying another layer of something that is meant for outdoors or do I have to remove the beeswax/mineral oil, sand, and start over?