Your seats are reserved. There’s no circulating air until the plane takes off, and even if you’re the first person on the plane, you’re going to be hot, you’re going to have to move, and you’re going to get elbowed — and maybe get luggage dropped on you. Also, if you’re not the first person to board, you’re going to spend 20 minutes slowly creeping down the crowded walkway.
So… stay out in the relative open space of the terminal waiting area until the gate agents make the final boarding call. Or, at a minimum, wait until they call your boarding number before rushing the gate.
No one like gate lice hovering around the entryway — especially as the rest of us are trying to board.