Has a life raft ever been successfully deployed in case of an accident?
Sure.  For example, Eddie Rickenbacker and 6 other people spent 3 weeks adrift aboard life rafts after their B-17 ditched in WW2. 

Read more -- https://www.historynet.com/eddie-rickenbacker-and-six-other-people-survive-a-b-17-crash-and-three-weeks-lost-in-the-pacific-ocean.htm