The key to fruit trees is knowing what you want. If fruit is a priority then your tree will require annual pruning to ensure good fruit production and accessibility. If you are more interested in having a nice looking healthy tree with fruit being secondary, then the tree will not require much pruning.
Summer prune for fruit
July and August are the best time to reduce the upright vertical growth (suckers/watersprouts). This new growth produces wood, not fruit. Suckers are the inevitable byproduct of trying to keep a tree small, in this case to access the fruit. Removing suckers in late summer will slow their subsequent re-growth, though your tree will always produce annual suckers. Suckers can be removed at other times of the year, but their re-growth will be more vigorous.
Winter prune for form
Too much fruit production can break branches and diminish the overall quality of the fruit. Thinning improves fruit quality and reduces branch failure. After thinning the overall shape of the tree will remain the same, unlike summer pruning.