Another data point to support the three year number being thrown about, this one from the founder of Yipit writing about their early struggles: "It took us almost three years to know what exactly we had to do during those three days."
Another data point : Amy Hoy mentions that her first webapp and those of two other people running SAAS businesses all took 2 years to hit 200k after launch - add on some dev time and it approaches 3 years.
http://viniciusvacanti.com/2011/09/12/the-long-grind-before-...