No safe word

Has anyone around here ever done a Ballbusting session without a safe word? Where the Domme could push you past your limits and you had no chance to end the session early? I'm currently thinking about making such an arrangement with my dominatrix - we know each other for quite some time already, she is very experienced and knows my boundaries. I just want to give her total control since I have the feeling that I can take much more than I'm normally willing to take. Has anyone had any experiences with such an arrangement? What was it like, did you regret it?