I had mine taken out 3 years ago by our dentist. He gave me valium to take before I came to the office, gave me some more valium by mouth as I got there, gave me the nitrous and novacaine and in 30 min I was done. I had a TERRIBLE time after with dry sockets so much so that my dh refused to have his out.
3 months ago dh had to have his out. He went to an oral surgeon, they gave him I.V. Versed. He woke up in the middle and said ooowwwww so they had to give him a lot more versed to get him out of it enough to continue. He was groggy for a few hours but was fine to go to work on Monday. He had it done on a Friday and he did well with no dry sockets but then he was stitched.
I don't think I could have 2 taken out and then go back and have the others taken out especially if I had a terrible time with the first 2....I'd never want to go back. At least if you have them all out at the same time you only screw up 1 weekend or week instead of 2.