I've oo'd and ah'd over the same question.
I found myself unconsciously meeting in the middle. Currently growing about 12 different plants, in different stages, and have given myself a personal limit of 12 plants (4 rows x 3 rows). From now on, I will plant more seeds every 2-3 weeks after each existing plant is harvested. I consider this a perpetual harvest, as fresh plants are already established/growing as its elder is completed, and the cycle goes on, like a conveyor belt. Its not a true SOG, nor is it pure large plants, its all 3 stages and cyclic. In theory anyway.
I limited to 12 plants as obviously the more plants the harder it is to justify, also its about my current limit of practicality. I'd rather focus on these 12 in a confident setup, than 24 plants in a half assed struggle etc. Greed has a lot to answer for, so I try to balance risk/reward.