For me if I buy any of these mobile and even if it works more than a year, I would be more than happy. Because after every one year, I feel like mine is the oldest model mobile in the world. SO would go ahead and change it.
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But lets see the long term ownership of the mobile, we will surely come to know the fate of the companies. But one thing is sure, that these companies have given a chance to people to buy Android bases high smartphones, who are having low budget as well. So salute to them.