On the economics of Seinfeld:
In this episode, Kramer is donating blood and saving it in a blood bank for future use. He becomes dissatisfied with high fees at the blood bank, and decides to keep it at home instead. In the meantime, Jerry nicks his jugular with an Exacto knife and needs blood. He awakens in the hospital with three pints of Kramer’s blood in him. This illustrates that when savers save, their assets don’t sit idle; they are immediately channeled to some productive investment most often by the banking system or another intermediary (such as the blood bank in this example), but sometimes through direct transfer (such is the case with direct purchase of stocks and bonds, and in this example, the direct transfer of Kramer’s blood to Jerry).
We do know that Sauron is capable of some degree of control over Mt. Doom, since it is said to be at his bidding that the cloud of smoke and ash covers the sky. We do not know whether he would be able to cause Mt. Doom to erupt at a moment’s notice, without first building up pressure, etc.
Even if Sauron can cause Mt. Doom to erupt immediately, we know from the actual story that the eagles are capable of navigating into Mordor and locating and rescuing Frodo and Sam, despite the major eruption which was taking place. Even if Sauron did manage to catch the eagles in the eruption, however, could this melt the Ring? If Sauron does manage to figure out that the eagles are carrying the Ringbearer, he might opt not to cause Mt. Doom to erupt, just for this very reason.