They accumulate stuff that will not be used again, taking up space you could better use for other things.

I wage a constant struggle against my own tendency to accumulate stuff.

If you are like me, you accumulate stuff: clothes, shoes, posters, books, furniture.

I have gone through life accumulating stuff, never knowingly throwing anything out.

Living to this age, you accumulate so much stuff — if you are a person who accumulates stuff, like me.