How do we know when the end is near?

Because dying is as unique as living for every individual, no one can know the answer with certainty.

Even seasoned medical experts who have a long professional relationship with a particular patient have been known to be off by months -- or even years -- when asked that poignant question about estimating the time left to live.  Still, if there is a knowledgeable medical expert involved, it may be worth the while to ask for a seasoned guess -- along with advice on other factors such as experimental treatments that may change the expectancy timeline.

And there are experienced caretakers with medical and practical experience who may be able to help coach you about what to expect in a particular situation. You may be able to get the best advice by consulting a local hospice provider, as such groups specialize in caring for terminal patients during their last six months or so of life. You can find a local hospice by using the search provided by the National Hospice and Palliative Care  Organization.