Sometimes in the early stages 1/second is as fast as you can go.

Practice, particularly on retreats, helps.

You can try to push the envelope by doing the following things:

1) Strip down the notes to just "bips" or "dats" or something like that.
2) Note the beginning and ending of things as two separate objects.
3) Realize that the instant you notice something, it is now something else and you can note that: you would be surprised how fast you can slice this.
4) Force the issue of speed by paying attention to anything tingling or even subtly vibrating at all and note every last one of them with the most rapid, subtle, quick notes you can come up with.
5) Longer and more sits.
6) Retreats, particularly 7 days and up.

Helpful?

Daniel