it will stay on your QC unless you specifically delete that capture from your library
sometimes it disappears from the Cloud because the user renamed or edited it and it’s still available but under the new name. Otherwise, if they remove it from their Cloud account, it’s gone for good there. But if you’ve already DL’d it, it’ll still be on your QC
It is probably best to do periodic backups of your QC in case something is lost. Of course, that requires you to restore as a full re-image of the QC device, but it is not too bad if you are doing the backups frequently.
We can also share our favorite presets to the NDSP Cloud, which would allow us to selectively restore content, and any captures are bundled with the preset. The one drawback, if I understand this correctly, is that the presets and captures remain linked to the original user. There may be problems if that user disappears or deletes their content, so full-device backups are still needed.
Experienced QC users - please correct me if I am misunderstanding the Cloud capabilities for preset/capture sharing.