Section. 2.
Clause 2: He shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur; and he shall nominate, and by and with the Advice and Consent of the Senate, shall appoint Ambassadors, other public Ministers and Consuls, Judges of the supreme Court, and all other Officers of the United States, whose Appointments are not herein otherwise provided for, and which shall be established by Law: but the Congress may by Law vest the Appointment of such inferior Officers, as they think proper, in the President alone, in the Courts of Law, or in the Heads of Departments.
Clause 3: The President shall have Power to fill up all Vacancies that may happen during the Recess of the Senate, by granting Commissions which shall expire at the End of their next Session.
.......
NOTES:
There are no time requirements or limits. He can nominate a person then confirmation thereafter can take years, if necessary. Eight members or less can make decisions. There is no one above the Court to say otherwise.
You are absolutely correct. Another thing in our favor is that the youngest judges on the high court are the conservative justices. So if the laws of mortality holds, the court will tend to be more conservative when vacancies occur.