There are lots of approaches to launching a product or company and many are based on the "big bang" of one event.  While major events serve a necessary purpose (as a target date/milestone) they in themselves do not dictate success.  This post from Seth Godin caught my attention and thought this part of the entry really nailed it.

"The best time to promote something is after it has raving fans, after
you've discovered that it works, after it has a groundswell of support.
And more important, the best way to promote something is consistently
and persistently and for a long time."