Recanting Euphorbia Obesa
Prior statements from me of gender changing E. Obesa and some additional information..
There is no time limit of how long a gender change would happen if such a change where to happen.
Sounding like the lines from the movie Jurassic Park
In a single sex environment gender changes may occur if a particular species is threatened to maintain a form of balance as long as it's capable of making a critical gender chance. A frog was used in reference during the movie
Assumption being that a single sex Obesa of one and only one could be threatened if the opposite gender of Obesa isn't present at all in a collection and may change it's gender in less time than one may expect for it's own re productive balancing and would also keep both flowering genders on the same single Obesa.