The youngest tree I have that I will hang from is a Plum tree, was around 20 years old when I started hanging. I could have hung from it MAYBE 5 years earlier, but it may have damaged the tree. Most fruit trees I have seen are soft wood, spending their energy getting big enough to produce fruit, then all of their energy producing that fruit, & not much energy producing strong wood.
I have a ancient apple tree, at least 50 years old, and a pretty young Blue spruce the same age. The spruce produced it's first cones 4 years ago. The apple stopped producing fruit about the same time. My 28 year old Oak has produced nuts for 3 years.
So, as mentioned above: Plant the fruit trees, & put up a few hammock stands among them.