Speaking from experience: :-)
You're correct, you can't be there at all times. Parental control software is just one more thing you'll have to set up and monitor. And kids figure out a way around it, QUICK.
When you're trying to teach kids - especially teens, who we're training to set free in the world - forcing their hand only makes them work harder against you.
We tried all this, including software, and none of it worked. Had a problem with a teen and video, killing our satellite bandwidth (which puts us in lockdown for 24 hours if exceeded.)
Warning one: We get another FAP, we unplug you for a month. Your choice.
Warning two: Next time, we cut the cable.
Warning three: there is no warning three. You have a job, get your own satellite account. You're done.
May seem a bit harsh, but as our kids get older, we aren't helping them by being a helicopter parent. Eventually, consequences are the only places real lessons are learned.