Comment by empiko

Surmountable, yes, but in practice it is often just too much hassle. If you are doing tons of these tests you can probably afford to invest in the infrastructure for this, but otherwise AB is just so much easier to deploy that it does not really matter to you that you will have a slightly ineffective algo out there for a few days. The interpretation of the results is also easier as you don't have to worry about time sensitivity of the collected data.