There have been times when my therapist has asked if something could be put on hold. After the dust settled, I could see that I had not been processing information very well or that there was a safety issue, but she was not heavy handed or laying down the law that there was a time limit on discussing a topic. Putting things on pause has been a good approach for those times. I can always go back (and do) rehash later on.

I don't think she would ever outright put a time limit on venting or say it could not be done.