I've done it twice, once where I needed to terminate with my first T, but wasn't done with therapy. A second time, many years after I ended therapy because I thought I was done. It wasn't my experience that it was starting from scratch, it didn't feel like wasted time although there certainly was a getting to know each other period. Both of my new therapists caught on really quickly, but maybe that's because I'm not much of a complicated person. I do remember being surprised how easy it was to just start talking with the new T's when they were new.

I don't think there's anything wrong with trying out the two therapist approach to see if it works. My preference would be to keep things more simple, and I would wind down with one T and get ready to see the next. When I was in this situation, I recall it as fruitful and interesting. The ending with T1, although I was sad to be leaving him, also felt like a kind of fresh start with T2, like I was graduating from elementary to middle school. And T2 was a really awesome therapist for me. I am just monogamous in all kinds of ways.