Starting months before my 65th birthday, my mailbox has been swamped with advertisements for Medicare Advantage insurance plans. The ads are still coming in. And then there are the television commercials with promises of Advantage plan benefits that original Medicare doesn’t cover – vision, dental, hearing services, rides to doctors’ appointments, zero premiums. Sounds amazing, doesn’t it? The advertising blitz surely has contributed to the doubling in Advantage plan enrollment since 2013, to 28 million last year. The plans are overtaking Medigap plans, which the nonprofit Commonwealth Fund estimates do not bring in as much profit for brokers as Advantage plans. It is true that the vast majority of Advantage plans provide some type of vision, dental and hearing coverage. And retirees with these benefits in…