Split Audiobook files

Usually it is the other way around and people are complaining about audiobooks being too broken up and wanting to know how to import them joined. If you have files that are 8 hours long then these are not standard audio CDs because those have a maximum of 80 minutes duration. It would help to know more about these CDs. If the files really are 8 hours long you will have to use an audio editor to split them up. iTunes has very primitive (actually not really by design) editing capabilities and the best way to do this will depend upon the format files you have.

Oh, I really am not familiar with those. Are they DRM protected? If they are there's nothing much you can really do about it. If they are not then an audio editor should work. Ideally use one that can do it without quality loss or re-coding which means something which can handle AAC/mp4-audio natively. I know something like MPEGStreamclip can do that kind of thing though it may be cumbersome and I don't know if it works under El Capitan anymore.

I guess one way to tell is to go to one and set a start an stop time in iTunes > preference then something like options (I use a different iTunes version). Then try to export to an AAC file. if you get an error message then it is DRM protected.

I am not very familiar with audiobooks and Apple and don't know if while Apple does not sell DRM music any more it may still sell DRM other formats (I know all movies are DRM). m4p does stand for protected but those are music files. I thought m4b meant audiobook format.

Very specific steps had to be taken to get non-DRM versions of old DRM files.

If they are DRM files then you cannot edit them or break them up other than whatever is available through iTunes features.