Although I'm sure that depends on the environment, it wouldn't be hard to get that in a best case scenario. The battery on my cheap flip phone lasts a week on standby if I'm somewhere I can get 4+ bars. A battery double the size would therefore last 14 days, which is "weeks"

Of course, if I leave the phone on at my house where I get about 0.000001 bars, the battery is dead in about 3 hours. I think it's safe to say that millions of people in India have better cell coverage than I do.