My rule of thumb is that it should take no more than 3 months to go from conception to launch of a new web service. And that's being generous. I'm speaking from experience here. I developed the first version of ONElist over a period of 3 months, and that was while working a full-time job. I developed the first version of Bloglines in 3 months. By myself. It can be done. And I suck at it! Just ask all the engineers who have had to deal with my code.