@kytta may not work for everyone, but I burn DVDs every so often with important stuff I want to preserve. Then, everything from that year-or-two(ish) goes into the disc and I know where to find it.

Or go frantically hunting through 3-4 discs till it turns up.

I do tend to organise things, in an obvious-to-me-if-not-everybody-else kind of way, so that helps, but I guess I haven't reached so many files that I need a better system to find them 😅