I doubt you are going to find much consensus on this.

it depends on how much time someone has to ride, the bike they are riding (some suck more than others on the road), WHY they are riding, just how far and how hilly it is...

If I was in my HT (which was not too bad on pavement) and just felt adventurous and wanted a ride with a little bit of everything... sure I might ride 5-10 miles to some trails.

But if I am in the mood for singletrack on my FS bike, I’m usually not going to want to ride the road long to get to the trails. The bike sucks on pavement, and the pavement eats through the soft, knobby, expensive tires fast.