Question for Fashionistas of older generations!

I recently became an Aunt, and have personally never wanted kids of my own, but have definitely been looking forward to being the cool eccentric aunt. I feel like a big part of that is fashion hand me downs, especially since clothes and fashion are a big part of my life!

So ive been wondering for a while now, looking at trends that come back from past decades, is there any pattern or indicators of a Trend or item coming back into fashion? Of all the trends you've lived through, looking back does it make sense which ones have come back into fashion or does it seem to be unpredictable?

I can't just hold onto my entire wardrobe forever so any advice on knowing what I should hang on to for future generations? Thanks!