Paediatrician says we can stop turning him back once he rolls both ways. I can't stop

Our son has started rolling onto his tummy in his sleep and staying there, face turned to one side. At the last visit the paediatrician said that once he can roll both ways on his own, we don't need to keep turning him back. He can, and does, all day on the mat. I still wake every hour or so, check the monitor, and turn him over anyway. Half the time that wakes him, and then nobody sleeps. The nights before an outstation demo are the worst, because I'm counting the hours till the airport cab. For those who've been through this: how long before you trusted it and stopped checking?