While they should spread some, your cookies shouldn't be super flat. This can happen if you add your butter while it's still too hot. Melted butter that's too hot can actually melt the sugar and will give you a greasy, runny cookie dough that will never hold its shape in the oven, no matter how long you chill it. On the other hand, if your cookies aren't spreading enough, it could be that you've over-measured your flour. Read my post on how to measure flour so this doesn't happen in the future!