That's how I remember it from high school - by the time the performance comes around you can play the piece without looking at the conductor.

I've heard that many pro orchestra/conductor combos only have one or two rehearsals, maybe the night before and day of the performance. In that case I could imagine it takes a lot of skill on both the conductor and musicians part to pull off the performance.

I found it interesting to hear that conductors didn't play a huge role until after Beethoven. The older I get the more I feel that post-Beethoven symphonic music is a little over the top and often hard to enjoy. Maybe the need for a conductor is a sign that things simply got out of hand. I do enjoy a good Strauss or Verdi opera, though, and that's even crazier in terms of complexity.