Your post took me back to when my late husband passed away with a similar condition.  Unfortunately cancer for some can be very drawn out.   
I think you should get in touch with a hospice who seem to know from experience what the time frame may be.   Until odd things happen and your husband loses a lot of weight or has pain etc you may not be able to get an idea.  With my husband he was in and out of hospital and the hospice for over a year because different things started to happen as the body starts to break down.  It's awful to have to watch and so I'm sending you my warmest regards.   Please look for support and help with Macmillan or the hospice , if the nurses on here, or ask your GP for guidance if you have a sympathetic one.... there is help out there.  

Nobody can give you a date but you may be able to get some idea.  
 

Hi Gballa

Im sorry to heat about your husband's diagnosis.

My beautiful mum was diagnosed with terminal Liver/Gall bladder cancer on 10th December 2021 and the doctors just said there was nothing that can be done and that was it!! They just left the room.

We pushed and pushed for more information and finally got to speak to the consultant who did give mum a time frame of life expectancy. It was a very tough conversation but time was precious so we needed to know.

Maybe speak to your husband's consultant and ask them to be honest, tno one can say when but they should know a rough time frame and they were correct with my mum.

Please enjoy every precious moment with your husband.

Sending you hugs xx