pinkruffles,
After you lay down your mixture, you could always go back every few months with a steel rake, garden fork or cultivator. Spot-check by lifting up or dragging aside enough leaves that you can see down to ground level.
That will let you know if they are getting objectionably matted. If they do, the layer is probably too thick, and you could drag half of the layer away. leaving the most composted bits behind.
Or just dig up or rake the layer enough to create gaps and openings so air and water can get through.
I suspect that people who warn against leaves matting down are using a very thick layer - say, thicker than 3 inches. Or some leaves may be more prone to matting than others, like oak leaves that break down very slowly.
<Edited to add: I see that people with more access to leaves than I do have shared their experiences. Trust their experience more than my speculation!>
