Hi Chris, a courageous try.
I have a couple of decorative silk fly line boxes in my curio, and volumes of between-the-wars Brit catalogs.


I can think of reasons not to keep up most antique fly lines, especially early postwar vinyl-coated nylon that copied coarse silk weave.
The fine-weave silk lines are worth stripping and refurbishing (unless they are mildewed).

A database could be useful for discussion
While I know many on the forum like old lines, I remember my first 444SL cracking and peeling after about 6 years.
There was also a NIB ebay purchase (apparently old stock) Canadian line that did this out of the box.