You have to prune them in winter, because they bleed terribly if you prune them when they are active. In the med, they grow it purely as a shade tree for the big leaves, and to achieve that they cut it back very hard in the winter - just to a very basic framework of thick branchels, or even pollarded to a stump. This also means, which is convenient when it is a street tree, they get no fruit off it to mess up the pavement, because fruit only forms on older wood with buds. So you can cut it back very hard and it will survive, but if you cut back too hard you won't get much/any fruit the following year. So if you want fruit, best to prune it every year or second year to keep it in control, so you don't have to cut it back too hard each year.

I prune mine tree with an eye to maintaining a few spots where I can lean a ladder. Because even at 12 feet tall you can't reach them all from the ground. I also encourage a weeping-willow shape to it, so I can stand in the middle underneath it and find a lot of fruit on the hanging lower twigs.