I am for sure in the "no such thing as over scouting" category, with a few caveats:
My play style is glacial, I enjoy the slow pace and working on my own wonders and helping my fellows.
I don't always *clear* the scouted provinces -- many of them lay dormant for events, especially on my primary city which has reached the cap on expansions from scouting. I know that some wonders use completed provinces as multipliers and that has some impact on my choices getting to where I am now, with 611 cleared. I'm at about 4 days, 11 hours and around 11 million gold per scout.
The major caveats to the "over scouting" camp --
=== difficulty clearing the scouted provinces (can be overcome with lots of patience and a great deal of resources devoted to the wonder support necessary but more realistically by building up a massive warehouse of goods)
=== the orc restriction, where you need orcs to scout but cannot yet produce them
=== main hall can't hold enough coins to scout the next available province (alt city found this out)