[CA Conservative]

By the way, it takes 67 votes to change this rule.

Not exactly. It takes 67 votes to change it during the Congressional session. However, at the beginning of the session, when the Senate approves the rules for the upcoming session, it can be changed with only 51 votes.

[Eagle of Liberty]

Not exactly. It takes 67 votes to change it during the Congressional session. However, at the beginning of the session, when the Senate approves the rules for the upcoming session, it can be changed with only 51 votes.

Interesting article:

How Robert Byrd Jr. created the modern filibuster

The major change in Senate rules that made possible the modern filibuster occurred under the leadership of Robert Byrd during his first stint as Majority Leader. Byrd introduced the concept of "dual tracking" under which the Senate could have two or more bills under floor consideration at any one time. Prior to this change, a filibuster ended floor consideration of all other bills until the one being filibustered had been disposed of. No appropriations, no nominations, no unanimous consent agreements, no nothing. All Senate business came to a dead halt during a filibuster, which raised the stakes on the members conducting the filibuster exponentially. The pressure that would be brought to bear if the entire Senate ground to a halt was one of the reasons filibusters were so rare.

Once Byrd changed the rules to allow dual tracking, filibusters became almost pain free. A Senator simply had to announce they intended to filibuster and the Majority Leader would use his dual track authority to move to other business and get around the road block. Over time, most leaders simply did a whip check and declined to schedule a bill if a filibuster was possible..

[Lazamataz]

True, but this is not the beginning of the session. It is the end. Now, if they attempt to do it at the beginning of the next, then you will have a liberally-permissive Senate but the Congress will shut them down.