And also one point which leaves some discussions: what is your opinion on helium-filled disks?
Today, they are nearly unavoidable at the higher capacities. So buy them.
A manufacturer generally designs to meet their datasheet and thats it - if a disk survives longer it is "just a nice benefit", ...
No, that's wrong, and way to cynical. Manufacturers first design to meet their legal and financial obligations. So for example, if a drive has a 5-year warranty, you can be pretty certain that it will last that many years, because the cost to a manufacturer of having to replace a drive (even after 4.9) years is way too high. Profit margins on disks are razor thin, and customer returns would destroy those profit margins.
Once a manufacturer has done that, they design their drives to be useful to their customers. Who are their customers? Not you or me. We have to remember that over 90% of all enterprise-grade disks are sold to less than a dozen customers (the usual suspects, FAANG and their Chinese counterparts). So Seagate/WD/Toshiba all design disks that the likes of Microsoft, Amazon and Google want to use in-house, by the million. What do the big customers want? Foremost reliability. While all of them use RAID-like techniques to make sure data isn't lost just because one disk drive fails (or just because a giant data center catches on fire or falls victim to a flood), the cost of having to store redundant information and of replacing disks is very high. Second, the big customers want low cost, over the useful life of the disk, including the cost of providing power/cooling/physical space for the disk.
And somewhere hidden in that sentence is the key phrase: over the useful life of the disk. Today, disk drives are not used for longer than 5-7 years, because after that the cost of providing power and space for the disk exceeds the utility, and it becomes cheaper to replace it. So I'm quite sure that very few 1TB disks are still in use, and 4TB disks are leaving very quickly.
So to answer your helium question: If you buy a new disk now, filled with helium, you can be quite sure that you will get good service out of it for 5-7 years. If you buy it with a 5-year warranty, it is very certain that it will not fail (again, this is statistics only). After that, you might get lucky, or you might not.
I use older disks as cold/archive storage which works fine - saving 160GB of data on 6 pieces of 15 year old sata 160GB drives just to give them some use.
For an amateur who doesn't care about space usage and for whom using computers is a hobby, that's a fine thing to do. I somewhere have a 40MB Conner SCSI disk that was bought about 35 years ago, I should see whether it still works. I also have a handful of 1GB Falcon/Imprimis class disks somewhere, which are probably the same vintage. But please don't expect manufacturers to design things so they remain usable after 30+ years; for them that is a waste of money, brains and time.
In re "bad experiences" the drives of various families from the same company are literally completely different beasts.
And this points out the fundamental problem of using the past (experience such as Backblaze) to predict the future. You can not extrapolate from a disk model 12345 manufactured in 20XY at manufacturing plant ABC having been very reliable to other models of the same manufacturer (different technology, different models, different plants) also being so. This is why people who study disk reliability for a living (there are dozens of us!) use very fine-grained data, for example tracking what manufacturing location was used for different components. So does this mean that there is absolutely no data about disk drive reliability? To first order, yes.
Here's my personal answer: Look at what manufacturer or model line does consistently well on publicly available high-statistics data, such as Backblaze. Do not listen to anecdotes from individuals (like me), because the plural of "anecdote" is not "data". On the contrary: experiences from individuals tend to be biased and blown out of proportion. If a manufacturer or model line does consistently well, for many years, you can then trust them on average to do better in the future.
Finally: GOOD BACKUPS. Your disks will fail.