A lot depends on whether the onions are short-day or long-day onions and the time of year that you plant them.
Do you know what variety of onion you have?
If you want to merely revive your green onions to extend their usefulness, you can always put them in the ground and use them as green onions (harvest as you need them). Sometimes the onions I use this way are ones that have gone yellow and spindly in the refrigerator. They revive quickly and are fresh and useable again in a month or so. I call these "zombie scallions".
