Elon Musk indicates that SpaceX will probably build 30 to 40 rocket cores for ~300 missions over 5 years. Then SpaceX BFR takes over and Falcon retires. The goal of SpaceX BFR is to enable anyone to move to moon, Mars And eventually outer planets.
300 missions over 5 years is an average of 60 space launches per year.
Building 30-40 rocket cores means 4 sets of 9 rockets would be able to be reused for first stage 75 times each for the missions over 5 years. SpaceX has said they would want to reuse block 5 rockets for 100 times. They would be used ten times and then have maintenance for another ten uses.
SpaceX will prob build 30 to 40 rocket cores for ~300 missions over 5 years. Then BFR takes over & Falcon retires. Goal of BFR is to enable anyone to move to moon, Mars & eventually outer planets.
— Elon Musk (@elonmusk) May 13, 2018