I've been seeing two Ts for about a year. The therapist I added is for EMDR and DBT (which are things T1 doesn't do) and discussing major relational issues that have come up with T1. I find it helpful to get two perspectives sometimes. T1 and I have been on a long journey of essentially finding and building up my core self, so that has been intense work and sometimes blows up in horribly painful ways. The other T helps me work through the blow-ups and build emotion regulation and distress tolerance. (She also sometimes validates that T1 has made a mistake when T1 is too stubborn to admit it and I'm feeling mildly gaslit.) It has been a really good experience for me, and it's generally not too difficult to remember what I have been talking about with each of them. I'd recommend trying it if you think it could be useful.