It's the trunk of the tree that become too large for the mechanical shakers to have sufficient effect. It will take many decades before the trunk reaches such dimensions. All of the trees on my farm are over a hundred years old, some nearing a thousand. The trunks and supporting branches of these trees are massive. The mechanical shaker would have no effect on them.I wonder what happens with the mechanical shakers after the plant reaches maturity.
Handheld mechanical harvesters can be used to shake thinner branches on mature trees. These can very effective and do not damage fruit as much as the big tractor like machines. But the highest quality olive oil is obtained by early harvesting, when the olives are still very green and hard. At this stage they are also attached very tightly and shaking a branch is not enough to make them fall into the nets. The olives have to be removed by hand. The shakers work best for mature, softer olives that are past their prime but render a greater volume of oil.
So how do you tell the difference as a consumer? First by the color, a real early harvest oil will be a bright and vivid green. A lesser oil will be yellow. You can also distinguish the difference by smell. A green early harvest oil will fill your senses with a strong aroma. And finally by taste, an early harvest oil, especially one that has been recently pressed, will have a strong peppery after taste. It can be very strong, so if you are tasting the oil, only allow a bit into your mouth, then spit it out and wash your oral cavity with water. If it burns a bit, you know you have good stuff if combined with the good color and aroma described above. This peppery quality will diminish over time, normally between 1-3 mos after pressing.
A good early harvest oil is abundant with flavor, and aromas. It maintains these qualities longer than a mediocre oil will. The catch? Harvesting olives early, when they are hard, requires all work be done by hand, and these hard olives render less oil. So? Its more expensive to produce...and buy! There are no free lunches in life my friends!
Cheers