Right now, after blooming.

Years ago we cut ours back to the stump hoping to kill them. No such luck. They grew back better than ever. We just cut whenever now.

Dont prune them flat, do it by hand and cut 1/3 of the branches off in a random pattern. Now is the time to prune.

Now, if you want flowers next spring.

If they ruin the shape, you can cut them off anytime. Just reach in and follow the errant stem to a crook at least 6 inches below the top height you want. If the plant is getting too dense and the center is dying, you may want to take that branch down lower and let some light into the middle.

I think you can prune now - right after they are done flowering

Our smaller (2' -3' tall) azalea bushes have long branches popping out of the top, making them look unkempt.
Do I just leave them alone or prune! Thanks!