I prune my plants generally up to the middle of flowering to concentrate the flowers and maximize the yield.
For everyone, but especially those who top their plants it is beneficial to prune your flowers that are not going to mature to worthwhile product.
Also, since light can only penetrate so deep into a canopy, lower flowers will never realize their potential and instead detract from what could have been converted into energy for viable flowers.
So here are some pics. I am adding the plants AFTER they were pruned (yeah sorry, no before their), then the pile that was pruned, and finally what you can expect those plants to look like at harvest. The big central cola is the size of a 1 liter bottle and their are 3 more that size that you can't see in the pic.