Apparently, You're supposed to replace your bras every six months, because with time and washing they lose their shape and ability to support.
I hang onto mine for not just longer than that (actually, I don't know anyone who does chuck their bras out every six months and replace with new), but for so long that the writing has worn off the labels.
But what really has spurred me into action is that the underwire on a favourite 'everyday' bra has snapped, the upshot being that I have a rather - er - lopsided appearance.
So it's off to Marks & Spencer to get re-measured - after all, I've been buying the same size bras since I was about 16, but that doesn't mean that I've been buying the right size.
The bra fitting service at M&S is by appointment (which I didn't realise), but it was early in the day, and the snow was keeping people away, so there was no problem there.
Over the next half an hour I was measured for size and fitted properly; then was talked through (and tried on) some different styles, and shown what I should look for (and what I should avoid) in terms of my shape and frame.
Marvellous! Well done, M&S!
I came away with a rejunenated bra wardrobe, and with the confidence to buy for my size and style next time round.
So, that's week 12 Challenge: done!
PS: That giant white jobby at the front of the pic is a sports bra - one look at my reflection in the shop window when out running last week convinced me of the need!