I got my seeds four years ago. I don't know how old they were when I got them. My germination rate has always been 100% for the ones I opened correctly. I ruined a few trying to get the caps off correctly. If you puncture the membrane under the cap, that one won't sprout. I use a thin bladed pocket knife to pry the cap off.
I also did not know that the ones with an even number of eyes were female trees and an odd number of eyes were male trees, so I don't know the sex of the trees I have in my greenhouse right now. They are 10 feet tall, and I keep them pruned.
I just started some new seeds three days ago, and have them marked as to male and female. I will replace my current trees with trees of a known sex, if they germinate. I just don't have enough room in my greenhouse to keep spares...
Good luck!
Carolyn