My notes from a talk by my godbrother - Siksastakam Prabhu:
Chanting is for our benefit.
In Mumbai they say if your rounds are completed by 7.30am you are like an express train for the rest of the day but if you don't finish them until in the evening it is like a passenger train... you will be slow and stop a lot ....!
99% of our spiritual advancement will come from our japa.
Like students of an exam we are told what the answer of the exam is (i.e.: chanting =success) and so all we have to do is chant.