Perhaps they are counting on logistics and support fraying over weeks, at such distances from the US homeland. 

It is not an unreasonable assumption - the USA DoD is the best in the world at this, but that doesn't make it infallible or costless. Doesn't matter how many planes are parked in the ME if they become unservicable.

There's also the prospect of Trump getting distracted, or falling out with Netanyahu.

Fingers crossed...