Outside wood? Is your sauna outside? Or the wood on the outside of the sauna? I didn't protect mine, just put it together from the factory. But mine is indoors

Outside wood? Is your sauna outside? Or the wood on the outside of the sauna? I didn't protect mine, just put it together from the factory. But mine is indoors. I think the wood will need replacing within the next 4 years probably, but the heater seems like it will last forever.