Waiting 2:30 minutes is not a big problem individually but it adds up to other builds the CI server is being paid for: we use a limited set of executors to prevent heavy parallel testsuites, so to counter that we'd need to reconfigure all other projects to use a different strategy to do resource control locking.

Shall we make a nightly build run it with that 'rake clean[all]' option?
I don't think we'll be changing gems on a daily base, especially considering that for some gems you need to login as root and install dependencies :-/

Would be ideal to be able to tell it to run the full (clean) build only when certain specific files have changed. Or like with Maven, keep a cache of downloaded gems externally to the project?