The manuscript autographs of the gospels and epistles have perished or been lost. How long would the average autograph last before it perished or became unreadable? Take Paul's First Epistle to the Corinthians as an example. It is thought to have been written sometime around 55 AD. No doubt, it would have been well looked after by the Church in Corinth, and many copies made. Given normal use, and a natural desire to preserve the autograph, is it reasonable to assume that it was still readable after 50 years? After 100 years? Longer, perhaps?
Edit: There is an answer here: "How Long Were Late Antique Books in Use? Possible Implications for New Testament Textual Criticism" by CRAIG A. EVANS Bulletin for Biblical Research Vol. 25, No. 1 (2015), pp. 23-37 See https://www.jstor.org/stable/26371610?seq=1#page_scan_tab_contents
Abstract: "Recent study of libraries and book collections from late antiquity has shown that literary works were read, studied, annotated, corrected, and copied for two or more centuries before being retired or discarded. Given that there is no evidence that early Christian scribal practices differed from pagan practices, we may rightly ask whether early Christian writings, such as the autographs and first copies of the books that eventually would be recognized as canonical Scripture, also remained in use for 100 years or more. The evidence suggests that this was in fact the case. This sort of longevity could mean that at the time our extant Greek NT papyri were written in the late second and early to mid-third centuries, some of the autographs and first copies were still in circulation and in a position to influence the form of the Greek text."
Evans says the evidence suggests that autographs remained in use for 100 years or more, and perhaps as long as two centuries.
I accept Evans' answer as reasonable. Does anyone have other information?