'Subjectivity', not having any objective existence, can never die - for therein is no thing to suffer extinction, nor can 'it' be born - for therein is no thing to come into being. Therefore 'it' must be eternal (aeternitus, that is beyond the concept of 'time').
Only objects can be born and can die, only objects can be perceived, only objects can be thought of or conceived, only objects can appear to exist. And all that 'exists' is appearance (phenomena) only.
About what is indicated by the word 'subjectivity' nothing whatever can be cognised, not because 'it' is some thing that is not cognisable, but because by definition 'it' is not any 'thing' at all. And yet, and inevitably, 'it' must necessarily be all that is and all that we are.
What, then, is it? No sort of 'what'. Just sheer phenomenal absence, whose absence is us (THIS which we are).