Is there any value to NOT deleting my own questions closed as duplicates? Does anyone benefit from me leaving these questions there dangling in infinity?
Yup: different people will word their searches differently. If you let the duplicate with your specific way of wording the question hang around, someone else may find it one day through Google - and consequently, the original question.
Closed duplicates are cool, because they all point to one original question in which high-quality content has accumulated over the years (well, supposedly).
Unclosed duplicates are a problem, as they are all cul-de-sacs and contain answers of varying quality, giving future generations no hint that there might be another, better answered duplicate somewhere else in the system.