The longest stint I've spent in Mumbai with work was three months. The contrast from my swanky hotel, air conditioned car and office compared with the life of so many in Mumbai was difficult, as was the contrast between the lives of those living in Bandra, Juhu and South Mumbai compared to the shanty town and the dwellers under the flyovers.
It was an experience, but not one I necessarily enjoyed. I will undoubtedly be back soon.