For ESTA duration Google has:
Your ESTA authorization is generally valid for multiple trips over a period of two years (starting the date that you are approved) or until your passport expires, whichever comes first*. This means that as long as you received an ESTA authorization to travel, you do not have to reapply during the validity period.
*If you obtain a new passport or change your name, gender or country of citizenship, you will be required to apply for a new travel authorization. This is also required if one of your answers to any of the VWP eligibility questions changes. The associated fee of $14 will be charged for each new application submitted.
I am guessing, but I doubt it is expected that multiple trips will all be to stay at the same accommodation - and were that expected I think safe enough to expect in turn that that would be mentioned.
The "generally" part may be explained by changes in circumstances, such as a criminal conviction or sexually transmitted disease that would invalidate an ESTA, rather than anything more mundane.