My husband has dementia. How do you know when a patient is in their final stages?

What is his current condition? Someone near death will become inactive eventually losing their appetite and close to the end will lose the desire to take fluids. End of life conditions can vary greatly depending on age, mental condition and many other factors. There's more info on this site regarding end of life and hospice care.

Thats very hard to say. Close to the end people often times go into a comma. The final stages can go on for a while and its hard to watch. If your loved one is walking about and talking its unlikely they are close to the end.