That's a red herring; the magnitude of this effect is usually greatly exaggerated, and in reality never comes close to being as important as the fact that flash memory is simply too expensive to use for cold storage.

And of course, the very idea of cold storage is dangerous: if you really want to ensure your data lasts for decades, you should be verifying your backups at least annually and making plans to migrate your data off any media that is obsolete and at risk of becoming hard to read using commodity hardware. This also entirely eliminates the above flash memory data retention concerns.