One of the secrets in this industry is a factor called "the high cost of waiting." It means the younger you are when you purchase the policy, the less you pay over the lifetime of the policy.
Here's a good guideline to use. It may vary by specific policies, but, overall, if your clients are 45 years of age now and they wait until age 65 to buy, it will be three times more expensive. There are two reasons for that. First, because the premium is based on age at the time of application and they are now older, it is higher. And, second, they need to take a higher daily benefit to keep pace with inflation.
In my client presentation binder, I have a page summarizing this concept. It has two columns — one is titled "Now" and the other column is titled "Waiting." Here's the copy I use: