Far too often, I'm seeing people increasing their halfopen limits in their BitTorrent clients without realizing just what they're doing.
They seem to THINK they're increasing their speeds, but they actually aren't.
The halfopen limit only limits the speed at which you can make outgoing connections. Having it increased is completely useless beyond about the first thirty seconds of starting a new torrent and gets progressively more useless as the torrent continues. If your client is set up and able to accept incoming connections, the benefit window shrinks to under 10 seconds.
Incoming connections aren't affected by halfopen limits.
The total number of connections you can establish in total isn't affected by halfopen limits, only the speed at which they can be established.
Your total speed is NOT affected by any halfopen limits.