The agreement never expires or sunsets. The agreement contains some time-limited restrictions on certain Iranian nuclear activity, but its prohibition on Iran obtaining a nuclear weapon and its submission to an aggressive inspections and monitoring regime are permanent.
Specifically, the agreement establishes strict limits on advanced centrifuge R&D, testing, and deployment in the first 10 years, and after the initial 10 year period, Iran must continue to limit enrichment to a level that is consistent with a peaceful nuclear program. Certain transparency measures will last for 15 years, others for 20 to 25 years, and some will last forever, namely its obligations under the IAEA Safeguards Agreement and Additional Protocol.
This deal in no way authorizes, allows, or encourages future Iranian nuclear weapons activity, which will always be prohibited under the Nuclear Non-Proliferation Treaty (NPT). If Iran every acts to pursue a nuclear weapon in violation of the agreement, the United States and its allies retain their ability to respond with any number of diplomatic and military options. And thanks to the agreement, America and its partners are now in a better position to thwart any break-out attempt given the unparalleled understanding and awareness of Iran’s nuclear infrastructure that the deal has already provided.