The Spartan leadership was certainly in a position to allocate land because of the enormous size of the conquered lands. So the devil’s bargain was made – land to the commons in exchange for their willingness to fight in phalanx formation.
It seems that the new structure would have been instituted in a single step because of its interdependency. The need for a new kind of army generated a new constitution and social system. Of course a constitution can be created as a single event while changes in a social system take time and generations to take hold. Even the governmental changes must have occurred over time. For example, the Ephors had to transition from advisors to the king to being elected by a citizen assembly which did not exist before the reforms.