Spiced Maple Cider

I want to brew a batch of cider for the holidays, and given that it's fall, this seemed like an appropriate combination of ingredients. I'm not sure how much maple syrup (or what kind) to use in the cider. I'd like the maple to be prominent, but not overpower the apple. How much syrup should I use per gallon of cider? Does the maple flavor tend to ferment out? If so, would I be better off using syrup to back sweeten the cider?

Thanks

Maple sugar would ferment out. No reason you can't use it but if you want the maple flavor, pasteurize it and backsweeten with it.

Why do some people add maple to their primary then?

There's a lot more to maple syrup than just the sugar. But fermenting does change the flavor of whatever you start with.
If you want it to taste like maple flavored cider, then stabilize and backsweeten.
If you want it to taste like fermented syrup and apple juice, then add it to your juice.
I think this calls for two batches.