Well, first, with CC3 you don;'t lose ANY detail on the map. Now, if you mean saving the map as a PNG/JPEG/BMP then yes, you will lose the details as that is the difference between RASTER graphics (BMPs/JPEGS etc) versus VECTOR graphics
SO, keeping your main map as a VECTOR/CC3 version, you do not need to overly worry about losing detail as you zoom in, and the file size stays relatively small.
If however, you are like me and you want to but copies of those same maps into a document you are writing up then you need to convert to a BMP/JPG/PNG format, and then you will be looking at huge file sizes.
So, do not overly worry about the size of your file size if you are working solely in CC3 as you will have ALL the detail you need