Take a look at your lights. Shadow castign lights always take longer. So I often will have a fill light not cast shadows saves a lot of time. Main lights always cast shadows with me. Bump maps take longer too it you reduce them below 10 then they render a bit quicker. Do you have clear objects what is the refraction index does it need one? These are things that woudl have minumum impact on your scenes' look.

The wit of a misplaced ex-patriot.
I cheated on my metaphysics exam by looking into the soul of the person next to me.