I am glad you will be seeing his partner. I know I was afraid to leave my long-time therapist, even though things really were not working. It is not really a good thing to feel the same way about your therapist year after year. I think it means you are not changing.
For example, today my t offered to give me his magic bullet (no comments from the peanut gallery, please!!). We often talk about nutrition, and I asked if he had one. He said he might even have an extra one. I think we had this exact same conversation a few years ago, and he offered to bring his extra one in for me, and I got like all goofy and told him no. But this time I was able to stay in the moment and say yes, I'm not afraid of what it would cost me to accept something from someone. I reacted like me, not like my mother and father's daughter, who was taught to always say no, never be a burden.
So hopefully this other t, since he is your t's partner, can maybe help improve your therapeutic relationship with your own t. My pdoc used to be a student pdoc who just happened to have my t as his supervisor for his t work (but not his pdoc work) - anyway we 3 were all seeing each other at the same time for a couple of years, and it was near the beginning of my time with t, so we weren't yet that close. Sometimes I would complain to my pdoc about him, and he would just say that wasn't his impression of the t at all. And vice versa I would complain about the pdoc to t. I think when we've been tricked and abused, this*helps, to have this kind of crosscheck. Good luck