There is a lot of disagreement re over the best time to prune maples. I tend to prune them in fall, as soon as the leaves are shed and the tree's structure can be clearly be seen. Fall pruning offers an advantage over spring pruning in that the wounds will be well- suberized by spring and won't leak sap, which attracts birds, rodents, insects that might further damage the tree. Suberin, a natural organic polymer produced by woody plants as a response to wounding, is often referred to as 'nature's waterproofing for plants' because of it's resistance to decay.
Al
I don't think there is a right way or a wrong way insofar as timing goes. Your tree is programmed to (literally) wall off any injury that occurs. For more re how that happens, use the search words "Dr Alex Shigo" CODIT (CODIT = compartmentalization of decay in trees).
