When I think about this question, I compare it to my own work. How often do I think about one of the many projects I am involved in, including the colleagues I collaborate with regularly on the project? For me it really depends on many factors and varies over time. It can be that I don't think about a project for days/weeks at all and other times I'm preoccupied with the same thing all the time for a while. And everything in between. This is how, I imagine, it may work for Ts with clients. It may sound impersonal but we are their work projects after all. I am pretty certain it's very unlikely that a T would never think at all about a client they have been seeing for a while, between sessions. I don't think it's coming from caring per se, more from being involved in something and having invested some time and energy already.