Broken spokes

I cycle a bit, so I've broken a few spokes. They way it usually works is either:

I'm riding along, a spoke breaks and I realise it right away; or
I'm riding along, a spoke breaks and the bike gets noisy or hard to ride because the wheel is now rubbing on the brakes; or
I'm riding along, a spoke breaks and only when I stop do I realise it.

These things have happened in some interesting places. When I cycle toured, I took this shifter with me just in case. It worked a bit better back in them days. A couple of times I was right glad of it when I broke a spoke 100k from the nearest bike shop.

Up until recently, breaking spokes involved actually riding the bike. But I have had spoke break just sitting there in the shed. I leave the bike for a while (years in some cases), come back and oops, there's a broken spoke.

What's odd is that these spokes break partway along their length, rather than at either end, which is usual for riding-induced breakages. I don't know what to make of this. I suppose I could take some photos, but I'm not too cocky about the fine detail showing up.

Now that I think about it, it was trying to get the freewheel off to replace these spokes that did my shifter in.