Updated:  5 Reasons why a 90-day Elimination Period usually makes the most sense:
1. Most medical insurance policies can pay up to the first 100 days in a skilled nursing facility.

If you need rehabilitative care (e.g. physical therapy, speech therapy, etc…) most medical insurance policies (including Medicare and Medigap) can pay up to the first 100 days in a skilled nursing facility.  With many of the better long-term care insurance policies, those days of care paid by your medical coverage can count towards fulfilling your Elimination Period, even though you did not have to pay anything for those days of care.

2. If you're going to spend 20% more premium for a 30-day Elimination Period, then you might be better off buying 20% more Monthly Benefit.

A 30-day Elimination Period usually costs about 20% more than a 90-day Elimination Period.  If you’re going to spend 20% more premium you might be better off buying 20% more Monthly Benefit rather than a 30-day Elimination Period.  For example, would you rather have a policy that pays $5,000 per month starting on day 31  –OR–  a policy that pays $6,000 per month starting on day 91?  The premium is about the same for each.  I’d pick the latter.

3. For chronic care, your out-of-pocket expense for those first 90 days may be moderate.

If you need chronic care, (due to Alzheimer’s, Parkinson’s, Rheumatoid Arthritis, etc…) your care starts off slowly and you’ll gradually need more and more care.  Since you need less care initially (for example you may only need a few hours of care each day for the first 90 days) your out-of-pocket expense for those first 90 days may be moderate.

4. Sometimes, family members can provide care during the 90-day Elimination Period.

Some long-term care policies will allow care that is provided by a family member to fulfill the 90-day Elimination Period.

5. Federal law requires that a tax-qualified long-term care policy pay benefits only when your care is expected to last 90 days or longer.

If your doctor certified that you were expected to recover in 89 days or less, a policy with a 30-day Elimination Period would not pay any benefits.  The policy can only pay benefits if your doctor certifies that your care is expected to last 90 days or more.