I've misunderstood the question , I thought you want mostly to store the energy within something for long period but what you're actually asking is if you could pre-set the energy to manifest in years time or even lifetime's ? The more the time [in the future the tougher this to be achieved] but the stone example still stands.
So to break even future trough your thought and explain things on a higher scale put it this way, first of all you will have to hold the energy on something , you can't just leave a bulb of energy and expect it to still be there or even 0.00001% of it's power that once had.
Human:
1. Posses ability to hold onto the energy for VERY LONG TIME
2. Not only the energy is within and like a steak in the fridge but that energy renews itself and grows every time you meditate.
Other Thing : There no such thing as a Energy Bank, if you truly wish for some whatever reason to let's say manifest something in the long future, then best would be to send that energy direct to Satan or any other God's you wish and see fit to, but you can make a deal with any of them to keep upon that energy or use same energy when the time would come as you see fit and They will do manifest that for you but then again, why would you even want to do that? It's a waste of time,effort,energy better using that onto yourself , for now you do not get unlimited time , once you get the eternity then you can get back to the so called magical stone.
Stone:
1. No utility just a stone
2. You can invest energy onto it, a lot, trough the higher most powerful mantra's such as Sun Mantra but it will not last for longer then a human body/ soul would.
-Just as a end note, it would at least be better to charge something with energy then leaving it vainly onto nothing basically but then again, remember, charge yourself up , nothing else.