Just my 2 pence on the subject. I never call anyone sir or maam or mistress. There are the odd one or two who I have known for a long time and who may have earned that title but even then I would only say it to them very rarely and only in certain circumstances.

The only one I call Master is My Master. Even then it was a while before I even called him Sir and a slow progression to Master - He would not allow it until both of us felt it was right.

I am not saying it is wrong for a submissive to call others sir or maam as a matter of course just that it is wrong for me. Everyone is individual and as such has to act however they feel is appropriate.

Just my humble opinion