Time required depends a lot on how the apples are contained... If you don't have much, and can lay them on a flat board, a few hours are sufficient. If in a bushel or in a pail, you need to mix them once in a while for them to thaw evenly.
Virginias are quite small, so won't need as much time to thaw.
Also if you wish to have some concentration effect, then you thaw them less to still have the core frozen when you press.
The best I can say is check them every half hour - once they become soft you can press.