Which BRANDED A/C has longest life? & whose After Sales Service is good? Experianced customer will know best!

I stay in khar (mumbai) INDIA. i am about to buy a window A/C , vijay sales has quoted LG(17,900/-), SAMSUNG(16,900/-), ONIDA(15,750) +300-350/- installation charges.
Out of the above LG A/C’S , do they have a track record of working for at least 7yrs? an experianced customer can answer as they must have wittnessed himself? Which company’s After Sales Service was the best? vijay sales,next or croma store?If the life of all the above mentioned A/C’S is only 5 or MAX 6yrs, then what difference does it make Whether we buy any A/C brand, a lower costing indian A/C like ONIDA, VOLTAS or carrier, bluestar whichever brand quotes the lowest price will do?What difference does it make wheather we select any brand when usage life is only 5-6yrs maximum?Also when an Exchange is made between an old A/C when buying a new one, the amount these companies deduct is max 3000/- only. If assembled A/C’s good in price,usage life same as branded, pls mention add & tel reliable co andheri-bandra