Monica, Having done hospice with both my parents and in laws I can only say that as hard as letting go is that doing so through hospice is a gift to them and the family. It allows you to offer them compfort and dignity and what more could any of us ask at the end of life?
Where the cancer has spread and how far, general condition, organ weakness and immune function can change the situation quickly. As many of these things are unknown it would be impossible to tell. However there are some signs that are generally seen at different points during the progression to the end of life. Be aware that it can come slowly or turn on a dime it is very situational. Here is a link on WebMD on the subject.
www.webmd.com/palliative-care/journeys-end-active-dying#1
We are here if you need to talk.