A big problem with using spices is that you never know exactly how potent the spices are. Are the old, new or low quality? I great way to dial in your spice flavor is to make a tincture. Steep some cinnamon (or any other spice) in some 100 proof vodka for a week or so. Then at packaging time, pull a small measured sample and add your tincture to taste. When you reach the right flavor profile, scale up the dose for your batch. This will really cut down on the variations between batches and give you total control over the beer. Just adding spices can lead to over spicing the beer. It's easier to fix if you want to add more than to try to dilute by blending beers if there's too much. There are lots of threads on making tinctures.