The correct answer is: "It all depends on you." If you can slam 3 cups of coffee and do 12 tables at your peak, you should do 12 tables (you'll die at the age of 34, but hey, you'll be rich!). For myself I just kept adding tables until I felt uncomfortable / not able to take enough time to evaluate decisions and then scaled it back one. I do believe you should cut tables when moving up in limits.