25 CFR § 166.208 - How long is a permit term?
(c) Permits granted for agricultural purposes will not usually exceed ten years. A term longer than ten years, but not to exceed 25 years unless authorized by other federal law, may be authorized when a longer term is determined by us to be in the best interest of the Indian landowners and when such permit requires substantial investment in the development of the lands by the permittee.
(d) A tribe may determine the duration of permits composed entirely of its tribal land or in combination with government land, subject to the same limitations provided in paragraph (d) of this section.
(e) A permit will specify the beginning and ending dates of the term allowed, as well as any option to renew, extend, or terminate.
The following state regulations pages link to this page.