Unless you have to do some crazy undercuts, you'll never need more than 3 axes. And even if you do, you can flip the part. A good Cam program and some ball endmills will do very complicated 3D machining.

We had a giant 5-axis Thermwood gantry router to make composite tooling - I think we used the additional axes only once - they are a lot more time consuming to program and can get out of tolerance much easier.