Exporting two pages in one PDF from a large document of pages

I create flyers A4 2page print in a single InDesign file (keeps the formatting the same for all) in the same document and set the pages to show front / back / front / back.... as the page numbers increase. However when I comes to exporting these, it's long to export two pages one after another for each single flyer. 

If I export as individual single pdfs they are single pages, therefore not front and back in one single pdf. 

If I export as one pdf, its one large file I need to spend more time on. 

Ideally if I can export pages 1 and 2 as one pdf file, then 3 and 4 as one file and so on... etc. 

Is there a script or technique available? 

Thanks