I am not aware of any specific studies that focus on a 30/30 cycle, but there's plenty of research that suggests taking regular breaks is good for you.

The ideal work-break routine is about the work you do, if you control your own time and, of course, what suits you best. For me, I’ve discovered that routine tasks, like writing documentation, do well with a 30-30 cycle. However, when I’m working on problem definition, such as programming and especially debugging, I need more focused time, but I do make sure to take a regular break every hour.