@Kamal ********
well, your visa is valid for 5 years, but it gives you a permit to stay for 180 days... Your permit to stay expires on day 180, so yes, you need to leave before that OR go to an immigration office to extend your permit to stay for up to another 180 days. This can only be done once per entry. Technically you can stay up to 360 days IF you get an extension. Up until now, no one really knows what will be required in order to get the extension (180 days has not passed since DTV was launched), but it will be possible to extend if you meet the requirments.