Continuations can be reused many times. With delimited continuations you capture the continuation as a function that works basically like any other function. With unlimited continuation you capture the continuation as a weird function that never returns but can still be kept as a closure-like thing and called repeatedly. The classic use of multiple continuation calls is “logic programming” or “nondeterminism” where for example you say “let x = choose [1,2,3]” and choose then arranges to have the continuation called three times (perhaps even concurrently).