The ObamaCare bill was passed as a "reconcilliation", not as a straight vote because Scott Brown's election put the Dems under the 60 vote level to stop a fillibuster.

Any bill passed under "reconcilliation" has an automatic 10 year maximum life.

The 10 year sunsetting of ObamaCare will occur on 23 Mar 2020 and the Federal portion of the Medicare expansion will stop, leaving the states to find 100% of the money needed to pay for it.