I am asking this question on behalf of a Japanese acquaintance.
In my opinion, "for the rest of your life" is a very common phrase, but "for the rest of your existence" is not nearly as common.
However, I took the time to Google "for the rest of your existence" and came up with the following results.
- "Live Out Of Shame For The Rest Of Your Existence" Bitcoin Sextortion Scam
- If you had to live by one Psych quote for the rest of your existence, what would it be?
- If you don’t vote for me for The Fame Games on July 14th you will have bad luck for the rest of your existence.
- The life you make for yourself is the life you live for the rest of your existence
I think that you could replace "existence" with "life" and it would not change the above sentences. However, I am not sure now. Does anyone know what the difference between "for the rest of your life" and "for the rest of your existence" is?