back in May, I flew MVD-GRU-MIA, G3/AA. I was in PE the G3 flight and one of the first off the plane. The walk to the next terminal took about the 10 min (though I walk very quickly), I would plan on the 15 min mentioned above to be safe. There was one family ahead of me in security and I made it through in about 2 min. If your G3 flight is on time, one hour should more than enough. Of course any delays could/will cause problems. An earlier flight will provide ease of mind let you enjoy the lounge.