Hi and welcome!

Booking multiple flights on the same route is a no-no and is against policy. Generally you should book the first flight you intend to travel on. Then, if you do not get on that flight, the agent will roll you over to the next flight while retaining your original check in time. Most times the agent will verify that you are there and cancel your listing if you are not there. Occasionally, if the list is really long, the agent will roll over everyone but this is not something that cannot be counted on.