5 is a good number, I tend to keep 5 handy. Once you divide the work between 5, it gets a lot easier on you, the axe, and the wedges. Plus, by the time you cycle through a hit or 2 on 5 wedges, the tree has had enough time to move and decompress off of the 1st. Otherwise you could end up driving 1 or 2 in faster than the tree wants to go. Accelerating something as heavy as a tree with poor leverage, coupled with wood compression and the hinge fatigue, can be a slow process. Once I wedged over a 20ft tall 3ftDBH log over to a steep angle. I ran out of wedges to double stack, and they were driven in as far as I could get them. The hinge fatigued 10min later and it fell. It already had what I thought was a dangerously thin hinge under 1", and I didn't want the side lean to send it towards some valuables.