@shoop1966 You want to ask some very difficult questions. When I worked on an oncology unit, most of the doctors told us they just couldn’t answer the question of ‘how long’ because they really didn’t know. Every person is so different and responds so differently. Pain is the main thing that prevents good quality of life. Talk with your wife’s doctor so they understand how important prevention of pain is for both you and your wife. Your wife may also decide that hospice is the path she wants. Dealing with chemotherapy is no fun and is exhausting.
I think the main thing you have to do now is to have a good talk with your wife. Find out what she really wants and then support her.
I’m so sorry you’re going thru all this. We’ll keep you in our thoughts.