Usually three years, counted from a date the Nebraska DMV sets: the date you become eligible for reinstatement after a revocation, or the citation date after a no-proof conviction. Some suspensions need the SR-22 only on the reinstatement date.
More detail
The DMV publishes the rule by type of action. Point revocations and court-ordered revocations, which is where a DUI conviction lands, carry three years measured from eligibility for reinstatement, so the filing outlasts the revocation itself. A conviction for no proof of insurance carries three years from the date of the ticket, and Neb. Rev. Stat. 60-3,167 describes that as a continuous period after the violation. Suspensions that grow out of an accident, an unsatisfied judgment, or a missed payment on an accident settlement need the certificate on file only on the day the license is reinstated. Employment driving and medical hardship permits need it until they expire, and an ignition interlock permit needs it until expiration where the vehicle is registered in your name only. If the certificate cancels while a requirement is running, the insurer reports it, the DMV suspends the license again, and clearing that takes a new SR-22 and a $50 fee; ask the DMV how the lapse affects your end date rather than assuming. Council Bluffs drivers follow Iowa instead, where the DOT counts two years from the first day of the action, as the Nebraska and Iowa comparison shows. The filing triggers table covers which actions lead here, and the DMV, not a count from memory, confirms when yours is over.