3 weeks without work is a nice feature so long as one has options/opportunities to work.
It is possible to earn a professional livable wage on Elance, however the professions for which freelancers are being employed via Elance are frequently menial / not complex software projects (and thus the wages are closer to $5-50/h as opposed to $100+). I am unable to find more than 11 jobs on Elance in IT that pay > $150/h. I receive about that many requests from companies by email weekly.
I don't believe Elance, as a platform, is conducive/setup to address involved problems which require rigorous testing & best practices to begin with. What Elance does well is aggregates supply and demand and provides a method of finding work.
I believe the best option is to build a network / partner with other agencies who have different skill sets and refer opportunities within your network. This is how we've been addressing the problem of continuous opportunities with Hackerlist. We partner with tons of independent consultancies with domain specific expertise and forward them work.
Also, freelancing picks up over time. Almost every client we've worked with has turned into a return customer (which we're really grateful for).