I'm not to sure about maple syrup but I have made some birch syrup and spring is auctually the best time as the resins are going up the tree. I'd drill about a 1 inch hole on a south faceing birch with a tap draining in a 5 gallon bucket and then plug the tree back up as not to kill it and then boil the impuriaties out of it and depending on how thick you wanted it depended on how long you cooked it. Its nice to say you've done it and can do it if need be but its really a pain in the ass and its a lot easier just going down to the grocercy and buying it over the counter.

Bobby