You acknowledge that fact and if you're making a severe change you either run a longer test or you break up the large change into manageable chunks (Google Maps

You acknowledge that fact and if you're making a severe change you either run a longer test or you break up the large change into manageable chunks (Google Maps is a great example of this). For something that is effectively binary and can't be changed incrementally the only way is to extend the evaluation window or make a call with limited information.