I was going to pull my sons pacifier at around 5 months, but when I talked to his doctor, he told me to hang on a bit and that 9-12 months was a great time to "break bad habits". He said that kids at that age still need to suck. I was a little skeptical knowing that I was the one that was going to have to suffer! :) (My Little Jack seemed very attached to it, hence my concern to get it away from him) But, lo and behold, my son is 8 months now and he takes his pacifier to go to sleep and within 10 minutes he pulls it out of his mouth and rolls over to sleep!
I also would rather not have him suck on his thumb. I know that they can self-soothe easier, but as a speech pathologist that I work with says: "You can get rid of a binky, but you can't cut off a thumb!") :) We are going to cold turkey him in another month or two. So, I think that if you waited a little, it wouldn't be terrible. But that is me. Mom's tend to know what is best for their little ones. So, I guess my advice is to go cold turkey if you are going to do it. It also helps if the only time that they get the paci is during bedtime or naptime...that way it isn't that much of a shock when you get rid of it. Good luck!