Originally Posted by LarryJ

The Washington Center sectors above were saturated. Low altitude, often approach controls instead of Centers, could accept additional volume but higher sectors could not.

You either go low now or wait and go high at some indeterminate point in the future. Going low will significantly increase the fuel burn so you have to have Dispatch run new numbers to see if you have enough fuel to do it. If not, you have to decide if it's better to wait for the higher altitude or go back for more fuel. Very difficult to make that decision because you don't have accurate estimates on how long each option will take.