I never changed a thing on my tune once all was said and done and drove it daily to work, to the gym, to the tracks I hit and so on. I ran as lean as 15.1:1 but know someone who went 15.2:1, he just gave up more timing.
Again I do agree that closed loop is the way to stay for most people, but with my own experience I do not believe for a second closed loop is exponentially better somehow. The only adjustment my car ever needed was done via the MAF. Open loop = set it and forget it, no worries about minute exaust leaks that go undiscovered for a week, and again better gas mileage in the right hands.
As for dyno time, it runs me $100 an hour, so 8 hour tuning sessions like some people do aren't in the cards for me. Wideband setup of my own would be very nice to have someday though.