I run 12 clones very often (3x4), and even then there are differences that make me pick one plant over the other for harvesting, like position in the grow space and soil being from the same 320-liter bag of DIY compost, yet the drinking habits are a bit different, making some of the plants leave a bit more water on the tray, meaning either the soil is absorbing more water or the plants are drinking more, all of these small differences leading me to harvest 12 plants over one week, rather than taking all down the same day. They grow until they are ready, dry until they are ready, and cure for a month! xD
Subjective opinions on, like, everything also need to be taken into consideration, meaning my average harvest is probably 2 weeks late if you would ask for a second opinion from some other grower.