I agree with DriGuy as usual. I found some support groups to be better than others and none of them could fulfill everything *I* thought they should be.
Several hours would be too long for me, no matter how good a meeting it was, I think. Support groups by their very nature are random, sometimes chaotic, sometimes very disturbing and an hour is enough! Regardless!
With that said, I went to AA meetings for several months in early sobriety and there was nothing anyone could have said or done that would have made me drink. That was a decision I made before I went to the very first meeting. I was D.O.N.E. with alcohol. I went to only hour-long meetings but I went to several different types - from speaker meetings to book-studies to discussion to beach bonfires. It's good to try a bunch of different locations and different groups of people. I found meetings to be interesting for the most part but I couldn't figure out a way to use the culture in a way that was helpful so I stopped going.
Still stayed sober, that was my own personal decision.