Tip for Maven 3 / Tycho users running on hudson.eclipse.org. You should set the following property in your job configuration on hudson (hit the Advance button for your maven 3 job).
This will force p2 which tycho uses to ignore the eclipse mirror list, and only download artifacts from eclipse.org. If you have other external dependencies it will still get those as well from other sites. This should drastically reduce the overall initial build time on hudson.eclipse.org.