This is a pretty big overstatement.

DO NOT USE AN SSD to store your data long-term! Solid-state storage has a very short, finite life-span.

This has not been true for years. SSDs are generally more reliable than HDDs except in write-intensive applications (and even then... It really depends on what exact models you are comparing). SSDs have a life-span mostly talked about in terms of TBW (terabytes written) rather than years for a reason, if they're powered on and not written too they'll last as long as or longer than a hard drive. (Note: Powered on regularly, SSDs can lose data if stored unpowered for a long time (months)). If you just have an archival drive you're not constantly erasing and rewriting data to, an SSD is a great choice. Reads also barely affect the lifespan of at all, so you can still access the data you want to protect (hell, write-lock the drive even and it'll last decades if powered on).

What you want to do is buy an even number of hard drives, plug them in long enough to copy your data to, and then unplug them and store them in a climate-controlled area. bout once a year, copy the data to a different hard drive

This is just plain silly. Yes, the mechanical wear of the drives spinning up and down means they'll die faster. But we're still talking MTBF measured in years. And replacing a hard drive that's barely used every single year? That's not just bad advice it's creating e-waste for no reason. Also note drives fail on a bathtub curve... If you have two good drives that lasted a year, you are increasing your chances of a failure by swapping them for two brand new drives... The best thing you can do for your hard drives is to not power cycle them constantly, any typical usage is fine. Also mechanical parts can actually wear out from disuse as well. Even archival services don't go to these extremes you're recommending.

If you really care about saving your data follow 3-2-1. 3 copies of your data (live, archival (external HDD or similar), off-site), two-different forms of media (HDD, SSD, cloud (yes cloud is an HDD or SSD but they have their own redundancy)), one off-site (in the event of a fire etc.)

Honestly 99.9% of consumers would be fine with a 2-2-1 scheme, 2 copies (live and off-site/cloud), 2 forms of media, 1 off-site. If you don't trust Google or don't want to pay for cloud storage, set up a server with redundant disks at a friend's house. Just keeping a second copy on a server with redundancy is plenty of fail over for most use cases. 3-2-1 is for data centers and businesses (and any cloud service you rent from will follow 3-2-1...) Let's not overcomplicate how difficult it is to keep data intact, if I tell someone to buy a new 12tb HDD each year they're just gonna give up on keeping it safe.