Once it is really warm we do that, but not as cold as most commenters have been saying.

We live in a Victorian, and when we moved in we got an energy audit (through nhsaves.com - rates are currently 75% off - you should do it, will definitely save you money) and all of our air left the house every 15 minutes, so no "freshening" needed.

Now that we've sealed up a bunch and insulated more, etc, I think we are up to one air change every 1.6 hours, so not too bad for a 140 year old house.