When do you throw it away?

Don't tell anyone, but I had a tidy up. No it looks worse, because I am halfway through, however,

I was sorting spools of thread, and I seem to have quite a few 'nearly' spools. These are clearly too little left to go back on the machine, ( though I have done it before...)  so how far down do they have to be to just get rid? Or do I keep them indefinitely just in case I want that one for hand sewing?

When do you get rid?

I am still expecting to keep all these. Madness still runs in this quarter!