It is hard to give the specific number of times that a comic has to change as there are various factors to consider. It can be two times or more depending on the nature and time period given on the publishing date. It will depend on the publisher and the experience as well as the editors too. There are those who can do their work perfectly and make a few changes while there are those who have to keep making changes. It all depends on the timing and the level of creativity which determines the time period.