http://www.motorsport-total.com/rall...6-Englisch.pdf

The total distance of the special stages shall be between 300 km and 500 km.
- A minimum ratio of 25% of special stages shall be respected on the overall distance of the event.
- There shall be no single special stage minimum or maximum distance. However, there shall be no more
than 80 km of special stages between visits to service parks or tyre fitting zones.
- No one stage or part of a stage may be run more than twice in a rally, super special stages excluded.
I think the 80 km rule makes it hard to make longer rallies. If you do 80+80 on a friday, 80+80 on saturday and another 80 on sunday, you get 400 kms, plus some km's for a thursday super special. Or if you can find enough long stages close to a service park, you may have time to do three legs on a day