Good point. I remembered the 90 days as I believe this is the max allowed in 1 visit and that the actual ESTA is valid for 2 years if you wish to make multiple visits.
The wife and I filled out an ESTA online no visa required. Easy to do and costs only $14 each. Up to 90 days travel and done automatically. Don't pay an outside company good money for something you can do for yourself.
https://esta.cbp.dhs.gov/esta/