Medicare Supplements or Medigap policies may be changes anytime as long as you are in reasonable health. What’s reasonable? “Normal” issues such as non-insulin diabetes, high blood pressure, etc. won’t cause problems. Heart and Lung problems along with the use of a walker may limit your choices.
Some states including California allow for movement to another plan without medical questions once a year. The “birthday rule” in California has saved my clients money as they can change to a more competitive plan annually. Recently a 70 year old with MS came to me. She was paying a small fortune for her Plan F. She couldn’t easily change without the birthday rule. She’s moving to Plan G and will save over $600 a year by being willing to pay the $183 Medicare deductible instead of having her current insurance pay it.
In other states including Nevada you need to be accepted by the underwriters at any company when you’re outside of the open enrollment period (usually when you turn 65). However, I was able to save a couple in Reno well over $1,000 a year despite some serious medical conditions.
It’s important to talk with an indepedent agent that represents a large number of companies to be sure you have the lowest price for the plan you desire.