I answered a question made by someone who has not been seen on the site since April 29, 2016. It's my impression that "accepted" answers (answers accepted by the participant who had formulated the question) will be retained, but that others may be deleted. As my answer has evolved on the basis of further reading, I've added to it, but the possibility of its deletion has required me to keep copies of both the original answer and all of my elaborations of it. Are there conditions, other than acceptance by the OP, that would preserve my answer (seen by 2K participants so far) on the site, and, if so, will they also preserve my own comments on it (which I've made to reflect its evolution)?
I think you are having a misplaced concern about the roomba, which automatically removes some closed questions with low views and no positive engagement. An upvoted answer saves a question from the roomba. There is no automatic process which removes old answers, apart from zero- or negative-scored answers on old closed questions.
Furthermore, if there is deleted content on the site which you have written, that content and its revision history are still visible to you. It won't show up in your profile or in search results, so you are unlikely to find it unless you have saved the URL somewhere. There is even a link in your profile to show your own deleted content which has been written recently (but not recently- deleted content which was written long ago).