There's usually a moment you notice it: the big Duplo bin hasn't been touched in months, your toddler's moved on to smaller bricks or something else entirely, and it's quietly taking up half the playroom. Deciding what to do about it is often the harder part.
Is it actually time?
A few signs it's genuinely moved on rather than just between phases: nobody's opened the tub in a couple of months, play has shifted to smaller LEGO or something else altogether, and you're the one thinking about the space more than your toddler is. If it's just a lull, there's no rush — Duplo doesn't wear out, so waiting costs you nothing.
What's worth keeping back
Before it all goes, a quick two-minute sort is worth it for anything with real sentimental weight — a first set, a favourite figure, something you built together. That's usually a handful of pieces, not the whole bin. Everything else can go as one mixed lot without a second thought.
Selling the rest
Once you've pulled out anything worth keeping, the rest doesn't need sorting, cleaning, or matching back to sets. Loose bricks, baseplates, figures and animals can all go together exactly as they are.