[Someone]

There’s a difference between expected value of number of days you’ll survive and the number of days a given fraction of the subjects will survive, but I don’t see either supporting the claim “If you do it every day, you have about 15 months to live”.

  (215/216)^450 ≈ 0.124

, so about one in eight will survive for 15 months or more. The “5% probability to live” time is around day 645 (about 1¾ years):

  (215/216)^645 ≈ 0.0501

the “half will survive at least for” point is around 5 months:

  (215/216)^149 ≈ 0.501