When Fedora Unity first started doing these so-called Re-Spins, the challenge ahead could maybe be explained like this:

When a user downloads a Fedora release and installs the distribution, the user will need to download and install a number of updates. The “older” the release becomes, the more updates will be available, and the greater the total download size of these updates the user will need to download on top of the download size of the original release media.

“older” is in quotes on purpose, because really for an operating system -or “distribution” if you will- being released every 6 months, “old” is quite a relative concept. The number of updates available however, at any given time during the release cycle, may range from 0 right after the release (which has never happened before), to the total amount of packages installed on the user's system (often over 2000). You can imagine the size of these updates ranging from 0 MB to an astonishing 2GB(!), only 6 months after the initial release. A single Fedora release has a support cycle of 13 months.

Some of us do not have the bandwidth capacity or enough data transfer quota to download this many extra, rather useless bits. In addition, some of us do not have an Internet connection at all, and those benefit from getting the updates through Re-Spins as well.

The use of updates in Re-Spins has several more beneficial side-effects, which we'll explain in more detail later on in this document. Long story short; If for some reason the software used to compose the media (the release) with does not work for your hardware or your specific needs, updated software incorporated in the composed installer images might resolve that problem.

This is the original challenge the Fedora Unity team resolved a long time ago, and is at the base of what Revisor does nowadays.