From what I experienced in the industry, ideally the project should follow Initiating, Planning, Executing, Closing process but as the project continues you’ll find yourself still going back and forth – but not to a degree that will significantly cause delays. If you think about it, it’s really hard to plan everything before execution and sometimes you’ll find that the plan that you thought was perfect failed execution and you have to go back and re-plan. Sometimes there are issues with pressure to meet dates which can cause these mistakes. While the general framework is still there, the transition is a bit more gray.