Just back from my 2 weeks holiday and have that the team were really productive. They have finished all the assigned stories few 1 week earlier then expected. So they went and added 2 more stories into the sprint (we run a 2 week sprint starting from Monday ends on a Friday). Come Tuesday I had a chat with a developer and looked at the UAT of the stories they added… ops…. Think they were a little too enthuseastic..
One of the stories had too many UAT for it to be completed in time as they thought they had till Friday until dev work. That is ofcourse not the case.. The QAs needed time to run the UAT feed back any bugs they had fix that and re UAT etc..
Estimate your dev velocity to be couple of day short of your sprint or your QA will be setting up a voodoo doll as they will have to work overtime to have things done 
