How long the wifi will last. Do I need to buy some data, or it has infinity wifi????

You need to purchase data separately.. its like purchasing a no contract cell phone where you have to purchase a monthly load for the cell phone... or else, it would be just a dormant cell phone, like paper weight. : ) For example, I got 2GB of data good for 2 months. There are other packages for data like, 1GB for 1 month, etc. Now the length of time that data expires depends on how much data you use in a given time period. For example, with my 2GB, I did some light usage like emailing, attaching of a few jpegs or word documents, browsing the web occassionally, took out only a few bits of data out of my package. At the rate I used it, like an hour a day for seven days, I used up less than a gig of data. If hope this gives you an idea..hope it helps.