I don't think it's necessarily ideal from a hunting perspective, but we will run our dogs on our property 2-3x prior to the season (usually not until September/October. By that time the birds are old enough to not have to worry about them getting caught by the dogs or anything.
We are out there quite a bit and I always have the dogs with me whenever I am out there working on projects, and so sometimes I can't fight the itch to go run them and see what we can kick up. I'm sure we would probably shoot a few more birds each year if we waited until the opener to stir them up at all, but I don't necessarily think it hurts the population running them around a month or so prior the the season - just educates them and makes them harder to kill hunting (I could be wrong on this, just my hunch).
To be honest, I get just as much enjoyment running the dogs and flushing birds at our place as I do shooting a limit, so the potential pleasure of doing so a few times in the early fall outweighs the potential downsides of educating birds for me.