Here's some additional info from Chris:

The NASDAQ timeline is the quickest. Factoring in securing the NASDAQ studio for listing day of is an additional concern.

Then you have to have the I-Bank and additional bookrunner's IPO and dealtimeline to fit in corporate access and roadshow work.

External SEC counsel and their timeline.

External audit and their timeline.

And most important running concurrent to all this is the SEC approval timeline.

MILESTONE					TOTAL ELAPSED TIME 
FILE REGISTRATION STATEMENT			3 WEEKS 
RECEIVE SEC INITIAL COMMENTS		6 WEEKS 
RESPOND TO SEC COMMENTS			6 WEEKS 
SEC CLEARANCE/DISTRIBUTE RED HERRING	11 WEEKS (prospectus without details like pricing put included)
BEGIN ROADSHOW				12 WEEKS 
PRICE OFFERING				14.5 WEEKS