The short answer to this question is: the month before you need to make a claim! But since none of us have a crystal ball to tell us when we will be having a stroke or heart attack, or be diagnosed with a debilitating disease such as multiple sclerosis, Parkinson's or Alzheimer's, we simply can't rely on waiting till the last minute to buy long-term care insurance.
The truth is that anyone, at any age and at any time in their life can have an unexpected accident or change in their health that they could not possibly have foreseen that will require long-term care. A couple of well-known examples of such a situation are Christopher Reeve and Michael J. Fox.
A majority of people tend to put this to the backs of their minds and tend to think that this will never happen to me or this only happens to other people
Unfortunately, many people think of long term care insurance as protection that is mainly for older folks. But that is simply not the case. In fact, almost 40% of those receiving long term care are younger than 65 years of age! This surprising statistic testifies to the unpredictability of such a need arising at almost any age.
So, I suggest that the best age to purchase long term care insurance is at the earliest age that you can comfortably afford the premium or have enough income and/or assets to protect that it justifies the cost of the policy. Another sound reason for getting long-term care insurance earlier in life is that the premiums are much less and you will most likely easily qualify for coverage, perhaps even at a preferred rate that will save you considerable amounts of money throughout the life of the policy.
Unfortunately, as we age and get older, most people stand a much higher risk of developing health conditions and problems that could cause them to become uninsurable at some point, or at least substantially drive up the cost of a good long-term care insurance policy. My recommendation is to avoid these problems by investing in LTCI at a relatively early age if you can.
And since the cost of long-term care is not covered by medical health insurance, it only makes sense to protect your assets against one of the most devastating threats to your personal finances. In most cases, the earlier you get coverage for long-term care, the better.