Great pics @Riversedgebonsai, I currently have 4 zones with 150 to 200 at each. I’ve personally lost track of count. They range between 3 to 7 years old or at least the ones on the spitters. The failed grafts then get wired up and allowed to grow because they get cut back around 2nd and third year in preparation for grafting. This as you said before promotes back budding on the lower areas. As the number of trees increase throughout the years, less and less space is available for adequate lighting. And by allowing the tree to grow too freely only weakens the lower buds and thus the slow process begins, balancing the upper growth with the lower. As for watering, the system is set up the water in the evening twice a day, first to penetrate the surface and 30 minutes later it waters again for a deeper saturation. If the power goes out I just turn the valve manually.
It becomes clock work and tiring at times, fall and winter- pull old needles, reassess, then wire, and repotting. Spring and summer- to cut or not to cut, and in the Texas summer trying to figure out when to decandle is the hard part. If future forecast is over 100 degree then I decandle early. I have to say the worst part is about 30 percent of my stock is corkback pines and if the lower branches die, I’m pretty much out of luck if anything back buds.