I told my T that if/when I decide to terminate, it would be in person because she deserves that much respect. Sometimes when I imagine self terminating out of frustration, having set that expectatation is liberating, other times it is frightening.

Your putting your T on notice of possible termination, even without stipulating the mechanism, is the mature thing to do and asserts your self agency. At the same time no T wants a voluntary (e.g., non court-mandated) client to terminate unilaterally. They want to be in control. And of course they want the income.

A continuing client is a known quantity. A new client is unknown. Same for us and the prospect of a new T.

Regardless of anyone's assessments or preferences, it's not their place to try and prevent us with veiled threats ("you'd better not"). Psychotherapy is or should be a consumer-driven transaction.

Best of luck working through this. It's really tough.