Liquidating a rental every 2 years and capital gains

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I keep hearing of investors who want to liquidate several residential holdings and avoid any capital gains by selling their primary residence then moving into another previously rented out home, which becomes primary, selling after 2 years and repeating the process until completly liquidated. They tell me they can completly avoid any gains tax using this stategy. One accountant I had told me no, I would still have to pay based on the profits after the basis was calculated. I got a new acountant and she told me that yes the tax code requires the tax be paid but that few pay because its not an enforced requirement. So is this one of those fabled loopholes that the rich have always jumped through? Because if it isn't then I may as well just sell all my holdings and pay the piper.( I want out because the mortgages are nearly paid and I've had enough of maintenace and tenants!)