The Secretary may extend on a regional basis the period for replacement under this section (after the application of subparagraph (A)) for such additional time as the Secretary determines appropriate if the weather-related conditions which resulted in such application continue for more than 3 years...
refund or for making credit or refund if no claim is filed, provided in subsections (a) and (b)(1), shall not expire prior to 6 months after the expiration of the period within which an assessment may be made pursuant to the agreement or any extension thereof under section 6501(c)(4...