My T and I both swear occasionally, but not a lot. We do it more now than at first, as we know each other better now and so can be more informal. I remember after months and months of seeing him, he swore in session and apologized ("excuse my French" sort of comment). I thought that was sweet. Now we don't feel the need to apologize for swearing, but just do it if the situation warrants it. For people who swear very little, like the two of us, when a swear word is used, it communicates a lot! (I would say it is less than every five sessions that a swear word is used.)