Is it ensure, insure, or assure?
also life-time, early 13c., from life (n.) + time (n.). One word from 19c. Old English had lifdæg in same sense, literally "life day."
lifetime life·time (līf'tīm')n.
The period of time during which an individual is alive.
The period of time during which property, an object, a process, or a phenomenon exists or functions.