A beer that sits for 10 days might not be at its best carbonation. All the particulate matter needs to drop out. Cold crashing/ time can take care of it. Otherwise when you pour it in a glass you Getty allot of head and not much carbonation in the glass of beer. Also. Wounding how long to shake/kick a keg? Shake it till gas will no longer go into it. You can hear the gas stop when you reach the max saturation that the beers temperature can hold.