I asked my T how she does this work without a break - she appears to let most clients roll past the 45 minute mark. It was bothering me - I worried that other people's stuff would slide into my session if she didn't get a break.
But she ended up explaining a bit of her technique and how she resets herself. I accepted her answer, I believe her that it is possible for her to do this. So, I don't worry about her now. I also discovered that I need to have the end of session be well defined!

So, have the discussion about the therapists job. And, I'd say go ahead and make the observation "It seems like you have trouble with your asthma". She may not want to talk about that so much - or maybe the client before you has a cat and it triggers her! She may not realize that your awareness of her wheezing breathing is a distraction, she may not notice it herself.