Most likely, all sectors of the virtual hard drive will be touched when the guest is running, so all pieces of the file(s) will have the current date/time as last accessed.
The benefits of splitting the virtual disk into multiple 2Gb sliced files is: file copying/archiving, shrinking, resizing. All operations like that will only need 2 Gb plus a small additional overhead on the host of free space. If you have the disk as a single file, you need as much free space as the max. size of the disk! Also, splitting it creates the disk descriptor file as a separate file, instead of embedded into the single file - making troubleshooting disk repair MUCH easier (the separate descriptor file).