Outdoor Wooden Staircase Treatment

[Michael Walker]

Hello!

I have a property in Maine with a 3-story outdoor staircase behind the building. This is primarily used for tenant access to and from their units, and has very little actual deck-space. 

The staircase is similar to the one in the picture however is much older and hasn't received TLC since I don't know when.

It's Maine - snowy winters and humid summers are a thing. The staircase is also facing south along a river / receives a ton of direct sunlight. Currently it appears in fair condition however the wood is faded to an almost muted brown/gray color which is the norm of all the neighbors. 

Question: What kind of treatment is necessary to assure the wood remains in good condition? Also - for stains - have other folks found stained outdoor staircases to be a good ROI?

Cheers.