What is the life expectancy of an old woman with renal failure, end stage dementia, incontinent?

Depends: If the renal failure is end-stage, and requires dialysis; but, refuses dialysis, then days. If incontinence and dementia are due to a stroke, then, life may go on for months. However, dementia of the alzheimer's type and the incontinence is merely stress urinary incontinence, the patient may go on for years.

Difficult to say: Signs that someone is nearing the end of life include weight loss, decreased speech (fewer than 6 words per day), need for medical interventions like IV fluids, frequent infections, not walking any longer and decreased interactivity with others.