How often does the same product go half price?

The short answer: for a lot of branded packaged groceries, roughly every four to six weeks. Not a law, not a published schedule, and it varies a great deal by category and brand — but it's a far better working assumption than "whenever they feel like it".

Promotional calendars are planned well ahead, negotiated between retailer and supplier, and spread across the year so that a category always has something on promotion without everything being discounted at once. The practical consequence for a shopper is that a product you missed at half price is usually weeks away from returning, not months.

Why this changes the question you're asking

Standing in the aisle looking at a half-price ticket, most people ask "is this a good price?" That's the wrong question, because you already know the answer — it's half price.

The better question is "how many do I need to get to the next one?" If the cycle is around five weeks and you get through one a fortnight, you need somewhere near three to bridge the gap. Buy one and you'll pay full price twice before it comes back around. Buy eight and you've tied up money in a cupboard for a product that'll be half price again before you finish it.

Where the rule of thumb breaks down

Four to six weeks is a starting assumption, not a promise. A few things reliably bend it.

• Seasonal ranges. Sunscreen, hot cross buns, cold-and-flu products and barbecue goods follow the calendar, not a rotation. Their discount pattern is about clearing a season, not maintaining a promotional rhythm.
• Fresh produce. Meat, fruit and vegetables move with supply, weather and harvest, which is why they can swing far more sharply and far less predictably than anything in a packet.
• Own-brand lines. Retailer-owned brands are already positioned on everyday low price, so they tend to promote less often and less deeply than the branded products competing with them.
• New products. A launch will often be discounted hard and repeatedly to buy trial, then settle into a slower rhythm once it has a place on the shelf.

The catch nobody mentions

All of this assumes you know what a product normally costs. And that's the quiet problem — almost nobody does, for more than a handful of items. Ask most people what they last paid for their usual laundry detergent and you'll get a shrug, or a number that's two years old.

Without that baseline, a rotation is unusable. You can't tell where you are in a cycle if you don't know what the top of the cycle looks like, and "half price" only means something relative to a price you can actually recall.

This is why price tracking exists as a category at all. Not because the discounts are hidden — they're printed on enormous yellow tickets — but because the reference point you need to judge them against lives in a place you can't get to: your own recollection of a price you paid five weeks ago and had no reason to memorise.