You can safely lower quality boost, trust me. You'll not notice the difference in quality in most cases and the difference in render times is just tremendous. If you see some blotches in the shadows, then it's time to increase quality boost.

There's another thing: the anti-aliasing strategy. By default, Vue 7 proposes Systematic and this is much, much slower than Optimized and, again, in most cases you'll see no difference. I just made a test render of just a sphere. With optimized on, it took 8 seconds to render and with systematic it took 55 seconds.