I’ve written a blog on Huddle about Speeding Up The Build.
It covers a few changes that can be made to help keep your build nice and quick (anything over 60 seconds I would consider slow). Ours is currently at 100 seconds, so we’ve still got some work to do. It’s not bad though considering we have around 40 projects, over a thousand unit tests, css/jss compression, and run aspnet_compiler as a further check.