From person to person, the time they spend shaking their cocktail may differ. No matter what, though, you will never need to shake it for longer than several seconds. Most of the time, intensely shaking the unit for 10 to 15 seconds will yield the results you are looking for. A good benchmark to shoot for is to shake until the unit is so cold that your hands literally can’t hold it any longer. For those of you who are looking for a more in-depth answer, there is scientific data out there to reference.