Unsurprisingly, it looks like we’ve already done it! (Mods, maybe separate this whole sticker part from this thread - it is actually useful information.)
I haven’t bothered with the convenience store stickers in several years - I used to go to coffee shops more often, but now the (rarer) Starbucks discounts are less appealing. I’ve never managed to use PX Mart stickers for anything - they typically seem to be decent discounts on overpriced products that I don’t want anyway. Got some good oven-safe ceramic dishes out of a Carrefour sticker promotion a couple of years ago. I vaguely remember the knife one at Wellcome that SuiGeneris talked about - that one was worthwhile, but I’d just finished getting the knives I wanted, so I didn’t bother with it. I think my wine glasses all came from these promotions too - maybe at Wellcome?