Tongue and Groove Decking

Southwest Missouri.  Shaded 8' x 50' tongue and groove covered porch. 

We will be replacing our current tongue and groove painted floor with a wider plank pine tongue and groove.  Our old flooring has rotten in a few areas and the cost to fix it is about the same as just replacing the floor.  Rotting was due to rain sitting in certain areas of the porch so we are trying to address those issues by angling the boards down when we install them and by installing a few drains in the flooring where we can sweep the water.  We will be screening the porch in.  What stain should we use on our new tongue and groove and how long should we wait to stain it?  We would really like something that is water resistant and that will last more than 2 years before it needs to be re stained.  We are open to all levels of opaqueness.