Open Enrollment Period: (as referenced in the Medicare and You Handbook): "The best time to buy a Medigap policy is during the 6-month period that begins on the first day of the month in which you are both age 65 or older and enrolled in Part B. [Some states have additional open enrollment periods.] After this initial enrollment period, your option to buy a Medigap policy may be limited.”
Applying with Someone in Current Household: Some carriers offer a household discount when applicants apply together (living in the same residence). To view the household discount rates click “Yes” and you will be given both regular and discounted rates. For some carriers, the household discount will only be eligible if both applicants are approved by the same carrier.
"Cost is usually the only difference between Medigap policies with the same letter sold by different insurance companies" — Medicare and You Handbook