You have 15 GB of Memories. What happens to them?

The 5 GB limit applies only to what sits above it. Of your 15 GB, 5 GB are protected and 10 GB are at risk.

Which 10 GB it is can come as a surprise. Snapchat keeps the oldest photos and takes the newer ones first. So it isn't your childhood that is most at risk, it could just as easily be last summer.

Roughly counted that is somewhere between 900 and 3,000 Memories in total, depending on how much of it is video. The Swedish broadcaster TV4 put the 5 GB limit at around a thousand photos, but a couple of hundred clips can weigh just as much. No exact figure can be given, and we're not going to invent one.

Anything over the limit gets 12 months of grace. Snapchat has not said when the 12 months start counting, and not what date the deletion happens either. Be sceptical of any page that gives an exact day, including our own countdown: it's an estimate, and we say so plainly.

To keep 15 GB with Snapchat you need their 100 GB tier. Snapchat doesn't publish the prices itself but points to the app, so you have to read the amount there. In the Swedish App Store, Memories Storage was 29 kr and Snapchat+ 45-55 kr when we last checked, without it being clear which tier or which period the amounts covered. The amounts are in Swedish kronor.

What matters is not the amount but the shape of it: this is a subscription, and it never ends. If you stop paying, Snapchat says you have 48 hours to sign up again before everything over the limit is deleted. A card that expires is enough.

It can still be the right choice. If you use the app daily and want the Memories feature as it is, with old snaps resurfacing from the same day five years ago, a folder on a hard drive won't give you that. But if you only want to keep the photos, you're paying rent forever for something you already own.

Snapchat splits large exports into several ZIP files of about 2 GB each. 15 GB therefore comes to around 8 files, with names along the lines of mydata~1784250848813.zip, -2.zip, -3.zip and so on.

All the parts are needed. They aren't copies of each other but different pieces of the same archive, and if one of them is missing, so are all the Memories that were in that particular part, without anything looking broken. Half an archive looks like a whole one until you go looking for something specific. With 8 files to keep track of, that is not a theoretical risk.

We count through the files for you when you pick them, and say so straight away if one of them is missing its counterpart, before you spend time uploading.

The finished archive is about the same size as the export, so around 15 GB. We don't recompress anything: the photos and videos come out in the same quality they went in, with dates and locations added.

15 GB fits on more or less any phone or computer. You can put the whole archive straight into your camera roll if you want it there.

The upload to us is almost always the slowest part. It is split into chunks and can be resumed, so you can close the lid of your laptop without starting over. Use a network cable if you can: wifi often halves the speed going up.

Pay Snapchat. The Memories stay as long as the subscription does. Simple, but never finished, and you are still left depending on whatever Snapchat decides next.

Do nothing. The 10 GB over the limit are deleted when the grace period runs out. Snapchat hasn't said which date, and anyone who gives an exact day has worked it out themselves, not read it at Snap. Deleted Memories can't be brought back; there is no recycle bin.

Get them out and keep them yourself. Asking Snapchat for the export costs nothing, and you can decide later what to do with it. It's the only option that makes you independent of whatever Snapchat does next.

Plenty of people do both, by the way: they pay in the meantime, get the export out at their own pace, and cancel the subscription once the Memories are safely on a disk of their own.