Particularly because there isn't a phase "Maintenance", haaaaa!
Phase 3 is Consolidation (where you add in certain things 6 days a week, always keeping 1 x PP...).
Phase 4 is Stabilisation (where, in the French book at least, very little guidance is given... except to keep the 1 x PP, increase oatbran, avoid stairs, and "off you go"... Lots have problems here because most of us have no idea what "normal eating" is... And so that's where some help often is required...
Before I started low carbing, I had stabilised for two or even three years, using the "80/20" system ("good 80% of the time, less so the other 20%)... while I lost weight before Dukan with "healthy eating", I had pretty much cut out bread etc., but I ate fruit and veg freely so had a fair few carbs going...
Now, alas, having messed around too much probably with my metabolism with real low carbing, and quitting smoking, I found that "95/5%" even resulted in an increase!! So that's something I need to work on... (because my 5% was HUGELY overeating)