I would say 5-7 minutes is pretty common for your sets while at tables, however I have stayed up to about 10 if it was a slow night or if it was getting towards closing time and there were a few patrons left at a table still finishing up a drink or so.
Remember: you can always go back to a table later if they request you to come back and you don't have other tables to entertain.
For the most part you hit them as soon as the drink order is taken for about 3 short effects and then move along to the next table. You will run into some situations where you might only get one effect in at a table and the food may arrive. Do not stand there and keep trying to entertain while their food is sitting in front of them getting cold. It is rude and awkward.
Sometimes I've even entertained between 2 tables and allowed them to both view the magic at the same time. As this isn't something that I typically do, I have had it happen.
You can actually avoid that if you just do one routine per table. Do a three phase ACR, end it give them the card, chit chat and then if the food arrives it's super easy to just step to the side because you are already done. Rinse repeat for each table and it will "seem" like you are doing different things at each table.