hmm shouldn't take that long unless your using oads of mental ray features? if its maya, swap to 2d motion blur, make sure your ray trace limits are like 2 2 2 instead of the default 10 10 20, unless your getting refraction through several objects its way to high,
mayas renderer is quick if used correctly, and even mental ray can optimised enoumously,
today i have been rendering HD 1080 frames with final gather and GI (pre-computed samples) i think it was taking less than 3 minutes a frame