In a visit, the time spent by a visitor to reach a page / fire a success event should also be availble as a metric. Would helps in understanding 'desired' vs 'actual' event completion periods.
There's a plugin, getTimeToComplete, that will actually do this. You just config the plug-in to track the time between two specific custom events. If you wanted it for each visit you could just fire an event upon the initiaion of a new visit and then fire the second event on whatever your conversion event is.