Oh what a lovely topic. Truly stunning characters, all of them, an extraordinary symbol of resilience and patience!
I agree wholeheartedly with the comments about seeing them in the nursery, it is quite shocking, but I am pleased to report that I have 88 mature olive trees in the garden here, most of them only around 100 years old, so babies by comparison, but they are doing just fine and, as far as we know, would have gone to the bonfire if we had not re-homed them.
The largest is this one, which we estimate to be somewhere around 300 years of age: