Just thought I would warn everyone about what happend to us.
We took out our ESTA before you had to pay for them. As we did not travel till 2 months later I assumed (wrongly) that was when it would start. Therefore I was surprised a few days ago to receive an email to say that it was running out next month. Thank goodness they did email me as we are going at the end of the month and I could have turned up without one. The annoying thing is my DH passport runs out in Feb 13 so his will only be valid for 8 months.