You can be there, or not. Chances we they won't go too crazy and will eat/lay down in the hidey. If you do floor time in the morning there's greater chance they'll actually run, since pigs are active then(or mine are atleast).
I do both, sit there or not. I tend to give them a full day on the weekend, and a few hours throughout the week. I've only had them full speed running once, in the am. Besides that the trot about, eat/poop and sleep. Try lining up tunnels and hideys for a race course they can zoom through, my pigs like to "scout" first, and then fly through the same way they just scouted. My cage is large for two pigs so maybe if yours is smaller you should consider more floor time, or not if it's big(mines 2x10).