Allen, after building oh a few of those, I know what it takes. Very Nicely done.
Not sure from the pic what kind of lumber that is, but I would suggest that if it is meant to be outside exposed to the elements. Be sure to seal up the ground contact points on your legs.
I have made several out of pine (not treated) several out of Red Oak and now I make them out of treated lumber.
The untreated ones last a bit over a year, outside, uncovered. The Oak ones are still holding strong as are the treated lumber ones.(going on 4 years)
If you will soak the bottoms of the legs in a sealer of some type for a few days, they will last a life time.