It depends on who is sponsoring your tourist visa and what is the relation of person coming to US wiht the sponsor and also the reason of coming to US. Anyways max time one can stay in US under Tourist visa is 6 month though they may give 5yrs multiple entry visa at max.

 You must have to have the return ticket not later than of six months if you coming to US under Tourist visa. I am not sure about after how long you leave US you can return.

Hope this helps you a bit and for more pls visit the site  http://www.usimmigrationsupport.org/visa_b2.html

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