What is maximum time duration up to which I can file TAX return for 2010? I am travelling back to my home country as my current assignment is over. And planning to file a tax return next year? Is it okay?

You can get an automatic extension for 6 months, so instead of April 15 you can file your 2010 taxes as late as October 15, 2011. If you are still out of the country as of October 15 you can apply for an additional 2 months, taking it to December 15 - see: Additional Extension of Time for Taxpayers Out of the Country. But be aware that any taxes owed by you must be paid to the IRS by April 15 to avoid interest charges for late payment.