ESTA visa in the USA
With ESTA you do not have to apply for a visa so that you can travel to the United States. However, you should note that ESTA does not meet the legal requirements that are needed to serve in place of a regular U.S. visa where it may be required. Just like the normal visa, when ESTA expire when you are within U.S. your departure does not get affected.
Duration of ESTA visa in the USA
Usually, ESTA application is allowed for up to two years or rather the date of passport expiry. This, however, does not mean you have to stay in the United States for two years. It can be used for up to 90 days per 12 months, so what does this mean? It means that if you have stayed in the United States for 90 days upon receiving your ESTA, then you are likely to wait for another 12 months so that you can start using it again.
The Customs and Border Protection have not yet set the exact requirements for the period one has to wait between the visits the U.S. If you wish to travel to the United States again after this period of 90 days has expired then you can simply apply for the U.S visa. And if you are seeking n immigration or any U.S information about visa, then you need to find the legal advice from a licensed immigration lawyer.
Make sure if your plan to stay in the United States will go for more than 90 days, you have a U.S visa with you. This is because you are likely to be banned from the program and also result in future refusals to get into the U.S border if you overstay with just the ESTA. Also if you visit the nearby country within that period of 90 days before going home first, then the days might as well count. Most of the travelers use this tactic, which has now been realized by the relevant authority and they are so strict on it.
While in the United States you cannot extend or renew your ESTA. What you need to do is to contact the relevant body before arriving in the United States, who will give you the go-ahead in case your ESTA visa in the USA expires during the 90-day visit. Therefore you should be careful when applying for ESTA to ensure that you get most of your travel and authorization upon visiting the United States.