Hey Lyn -
SO happy to hear that they finally settled on a treatment for you, and that your med onc is willing to "take advice." You are a GREAT "sifter" of info, and are basically encyclopedic on your string of skirmishes with your cancer.
As for the time element. I was on a trial for hard-to-treat mets with a huge invasion in my liver and some asymptomatic "haze" in my bones. When I went on the Taxol, Navelbine, Herceptin combo weekly, it was until any of the following occurred:
1. I had a complete response (best outcome! - my result)
2. Had to go off treatment as unable to tolerate it, or tumors continuted to grow necessitating a change of treatment.

We had a "hoped for" time of about 6 months once I showed some favorable response. There was no rushing my med onc to take me off. After the last CT scan showed only a few small spots, I had 3 more rounds, then a PET scan to show NED. At that point I was released from further chemo.
Basically, I would imagine you are on this treatment under the same guidelines as my trial.
GO GET 'EM!