I worked with a client who was dying of cancer. A few weeks before his death, he decided to hire me to prepare his will and powers of attorney. I traveled to him because he wasn't in a position to leave the house, brought my portable office equipment, and we talked. He usually took pain medication for the cancer but during my time with him he had to abstain from the heaviest doses so that he would not be under the influence of narcotics when it was time to sign.
An estate plan is an incredible gift you can leave your family so that they're able to care for you during your life without court intervention in the form of guardianship and a smoother transfer of property after your death. Don't wait until you're older. We can't predict accidents and illness so take time to plan for the unknown while you're young and healthy.