Only one direction right now.

It's show-accurate. They had to disable the gates and re-dial from whichever end they were trying to depart from in...at LEAST SG-1, I'm pretty sure Atlantis too. I forget why, exactly. Either way, going through the 'exit' point while it was still active had the lovely side-effect of killing people.

Sticking your hand into the Exit portal after you exited the portal, would keep the portal open longer then the auto cut off. At least in the Shows, SG1 & SGU.

That's true, sticking your hand in was fine. But I believe the show more-or-less established that if you went ENTIRELY through to the point that you'd be stored in the buffer to be forward to the exit gate, you'd be torn apart. Or...y'know. Something awful at the very least, given that they always had to re-dial when they were making a quick return to somewhere, rather than just running through the gate again.

You can always force the gate to disconnect instead of waiting the five minutes for it to auto disconnect.