Here in Tucson, Arizona I started out building my supers with various waterproof glues and galvanized nails. In other areas of this country, that seemed to work just fine. But I finally gave up on that fastening system, I then tried galvanized ring-shank nails, but despite the glue, even the ring-shank nails soon walked out of the wood (lots of temperature change day vs night). I had some coated deck screws (3-1/2" long), left over from building a wheel-chair ramp for my wife. I used some to assemble supers. I first clamped them tightly together, making sure they were square, then pre-drilled 1-1/2" long pilot holes. Using a drill or power screwdriver I drove the screws in nice and tight.
This is the beginning of the fourth year since I began using coated deck screws to hold my supers together. Some of the screws in the oldest ones have loosened slightly. A quick twist with a power screw driver and the supers are again firm and tight. When I tried doing this same thing with nails that had walked out, it never succeeded, the nails would walk out again within a week or two. It costs much more than nails to use coated deck screws, but money is saved by not needing to use glue, and the increased versatility of using this method of fastening. I will continue using them until an even more practical fastening method presents itself.