If your passport was lost, stolen or has expired and you have recently obtained a new one, you will be required to apply for a new ESTA travel authorization before traveling to the United States.
Applying for a new or renewal ESTA is also obligatory if you:
An approved ESTA is valid for 2 consecutive years, or until the passport it is electronically linked to expires. Whichever comes first. During the validity period of your ESTA, you can go on multiple trips to the United States, without having to re-apply for a new travel authorization. However, you may only remain on US territory for 90 days at a time.
Note that there should be a reasonable amount of time between your trips. This is important so that the Customs and Border Protection (CBP) officer doesn’t think that you are attempting to live in the US. There is no specific requirement for how long you should wait between each visit.
Note: Should your ESTA expire while you are in the United States, it will not affect your departure in any way. (Click here for more information about the ESTA expiry)