I have kept several things from DS' babyhood, they are stored away neatly and i don't trip over them every day. I wouldn't like to narrow it down to just one outfit, if i chuck 99% i might as well go the whole hog and chuck it all.
Kinder egg toys are sorted through. If DS plays with tjem a fair bit and they aren't the instantly breakable things, then he keeps them in a little bag. Every now and then i'll take the bag on an outing and he plays with them as we have lunch (he is 5yo and can still get bored in a cafe). He rediscovers them all over again.
I am quite ruthless with his toys and tat doesn't last long. If a giift is not played with, it is regifted or charity shopped. If parts of a toy/boardgame get lost or break, then it is gotten rid of.
Having said that, i often repurpose old toys like the baseboard of a boardgame, or use the figures for something else.
Every so often i buy DS a bottle of water in a themed bottle (Darth Vader, Eeyore, Playmobil knight, R2D2 etc). I have collected 9 and 1/4 filled them with sand. They're kept in a box and we play bowling with them. Darth Vader 5 points, Eeyore 3 points etc then count your points. I've had the 'game' 3 years and still not bored!
But expensive bucket of wooden meccano? Not played with > gone. Wooden kitchen and playfood that took up a ton of space wherever it was. Not played with > gone. Bucket of soldiers found for 50p in a charity shop, played with for 1 day last month --> back to the charity shop.
I wait until he is at school. He doesn't notice 99% of the time. If he dors notice i adk him when the last time he played with it was. Then i tell him the toy has gone to a child who now plays with it a lot and he is fine with that.
I try to live by that rule: do i use it? When was the last time i used it? Would someone else get more pleasure from it? --> gone.
It's liberating!