Recently, we have had some questions on why their build is taking a long time. The system currently finishes one compilation before starting another. As a result, if you start multiple builds for the same app, it will incorrectly report how much time is left since it is waiting for your other build to finish.
We will fix this in the next release to either kill the previous build or correctly inform you how much time is left. For now, the work around is just wait till your app build is finished before you build it again.