I think that it'll increase naturally the more you write them. So assuming you write your characters on paper when you review them, your speed will grow naturally as the days pass.
Looking back at my "heisig review booklet", I can clearly tell that the first couple of hundred were written very carefully, and slowly and neatly etc, but as I flip through the pages I can clearly notice them getting more chaotic but fluent, and now I can write a kanji pretty damn fast, depending alot on the complexity of a character. I guess about a second maybe, for medium complexity kanji?
But here is one piece of advice: take your time when writing out the characters. Don't rush through your reviews. Your writing will suffer. Also take a look at this book:
http://www.amazon.com/Learn-Write-Chines...0300057717
It's not really about learning kanji (or hanzi in this case), it's about learning to write
properly. Don't necesarily do the entire book, just read the first dozen pages or something, to get an idea what you
should be doing. Heisig is REALLY vague on different types of strokes, endings, etc. You can find the book through various, less legal channels if that floats your boat.
Good luck on your kanji journey!
Jorre
Edited: 2010-12-31, 5:26 am