Hiya. 

I'm so sorry for your situation; im in this boat too. My FIL was diagnosed with 10+ brain mets from primary lung last May, declared terminal and untreatable in July 2018. He was given 8-12 weeks to live, and shouldn't have seen November, but he's still going. He was up and about but with some cognitive issues at Christmas. Getting words muddled, that sort of thing but largely okay.  

It's so unpredictable, it's really difficult to tell how long and with what symptoms. The information we've been given hasn't been anywhere near enough for us to plan with but our plans would have been shot out of the water anyway as he's lived so far beyond what we were initially told.

Our palliative care team are now saying weeks left, not months. He's in bed mostly. I think he's gone from being in bed until 1pm to only coming donwstairs twice in the last week. He's Confused. Stuttering. Starting to eat a lot less, and as of last night having vision problems. Most of these issues are intermittent and there are the odd glimpses of lucidity. It's awful to see.   

I'm posting periodic updates on his condition for just this reason - there are no details out there about how things could prossibly progress towards the end. I'm hoping the information in my posts might help someone else at some point. 

Love to you and your family. x