Hello cazmark and welcome to this forum.    I am sorry your mother in law has been struck down by this wretched cancer.  I have had a few experiences of caring for terminally ill cancer patients and to be honest there were large variations. And then again some gradually went downhill over a period of time and others suddenly crashed and passed on.  My mum went downhill gradually over a three month period from diagnosis until she died.  My son's dad started to decline gradually over two months then died unexpectedly in his sleep one night.  I should talk to her doctor, ask his/her opinion but you will only be able to be given a guesstimate.  But you will be watching for symptoms of your mum-in-law slowing down.  Such a very sad time.  I would also say to make use of this time, say things you want to say.  How is your mum-in-law at the moment?  Annie