When you prune back a shoot, the apical bud's (the bud at the tip of a branch or shoot) hormonal influence is lost and some or many of the lower buds sprout into new shoots. If you prune back "hard", many buds may sprout and race toward the sky. This shoots are what some people wrongly call "water sprouts". In fact they are just vigorous shoots with apical bud dominance. If you wait until next spring to prune, you may stimulate more growth with less fruit. You're on a pruning treadmill. Each spring brings more growth to cut back. (Great job security for a hired maintenance gardener!)
You get off the treadmill with summer pruning. As a tree's growth approaches late summer—August or later in mild winter areas—the new growth of the season slows down. Clipping the apical bud at this time is less likely to stimulate unwanted so-called "water sprouts". And clipping back to a new side-shoot or branch is likely to allow the shoot to grow out away from the tree without very many vertical shoots, to form a reasonably wider tree.
Now for the next rule of pruning: A limb growing at a 45 degree to 60 degree angle has the best balance between new growth and fruiting. A vertical shoot furthers its own growth. A limb pulled down to or trimmed to a horizontal position causes many of the dormant buds—buds that are neither fruit or shoot buds, not just the dormancy of the winter—to sprout into vertical "water sprouts". Placing or pruning a limb or shoot to the ideal 45 o to 60 o angle allows for some new growth but also favors fruiting buds lower down on the shoot. Pruning back to a side shoot at this ideal angle will promote growth—more so in the summer than the spring. These guidelines are best for shaping new trees. If you need to sculpt an older tree, you may have to sacrifice some fruit for a few years until the tree is in ideal form—can't have everything.
For older limbs I use a one-inch by one-inch board with a nail in each end to bend the limb 45 o to 60 o. (See photo.) Cut various lengths of boards, pound a nail part-way in on each end, and clip the head of the nail off at an angle to have two sharp points.
So, put on your shorts and tee shirts and prune and shape away!