Musings on past Oaths

I have had the opportunity for the past few days to consider, some of the past Oaths that I have taken in my lifetime, from the oath of Enlistment I took 3 separate times,to the oath I took the day I got married,and the day that I became a member of the local Search and Rescue Unit, i also have had reason to think about the reaffirming of my oath to Oath Keepers.What has me thinking is exactly what is an oath and exactly how binding will it be be if taken between just 2 people , a group that its officiated for , or simply a solitary promise one makes to themselves.
Now some of you will see , that some of these oath may not apply any longer , like the one to the S&R, i left that organization a few yrs back due to my health so am i styill bound by it?most would say no and what about my oath of enlistment , my military obligation was filled long ago, and i have been discharged from active duty and any reserve commitments, so do those oaths still apply? or can I change them , to fit my current status? I have no Officers appointed over me , I no longer fall under the UCMJ, so are those parts void? What about if i disagree with the President ? do i still have to follow those orders?
So does circumstances change the validity of an Oath?can one change that oath after the fact, because you see , none of these oaths has any time limit , or expiration date, most would assume that once the reason for the oath were completed that the oath itself becomes void, but does it ?Some veterans i know , both enlisted and officer corp , tell me no that the oath is for life, though almost to a person , they do agree that the oath is to no person, but to a piece of paper,the Constitution.
For me , there has not been an administration , that if i had to that i would , or could swear an oath, like the one i took for enlistment,not since i was honorably discharged but i could and still can swear an oath , to protect the US Constitution from all enemies , both foreign , and domestic , and after all isn't all oaths , a promise? to oneself ? what do you think?