When searching long, aged threads, I simply use my initiative to locate the exact year I'd want to read. It's not too weary as you described to trace back to a specific year—just click on the middle page number—then trace upward or downward depending on the opened page's year. If a Jump to function is added to the forum, you'll still need to do the finding yourself.

Edit: Threads like WO can be too weary to trace

You can achieve what you want to do with the help of "ninjastic.space ^{[made by @TryNinja]}":
^{- As far as I can remember, I've never failed to locate something with this tool.}

Steps: Go to the Post tab > Copy the topic ID > Type the keyword in the Post Content field > Set the Date Range > Click Search.