Geo, I assure you, this gate will NOT sag.
First of all, the frame is out of full 2" thick stock.
Second, there are three 5" x 3/4" oak dowels set at each butt joint.
Third, the hinges are very heavy-duty.
Fourth, I routed a recess that the four "L" brackest fit down into so that they are flush with the surface of the gate.
Fifth, the "L" brackets on the hinge side of the gate are exactly opposite the hinges. The fastener heads you see are actual bolt heads, not lag bolts. The bolts go through the recessed "L" brackets, through the 2" frame, and then through the hinges on the other side where they are held on with lock wasshers and nuts.
Sixth, the posts they are attached to are 4" X 6" posts that are set 36" in the ground. I weigh 200 pounds and I can hang all of my weight on the gate and it doesn't budge. Also cedar is very light.
I had a fence company install the fence, but I built the gate just for that reason, I didn't want it to ever sag.