If you decide to work past age 65 and have an employer-sponsored healthcare plan, you can model delaying Medicare.
1. Go to My Plan > Medical
2. Scroll to "What will your out-of-pocket costs be after you are eligible for Medicare?"
3. Click on "Estimate Projected Medicare Expenses."
4. Click on "Yes" for the question "Will you have employer-sponsored Medical care?
5. Enter your annual out-of-pocket costs and the age these costs will end.