The Seagate Ironwolfs 18TB have a Workload Rate Limit (WRL) of 300TB/year, as do some WD models. Unlike SSDs this WRL includes not only writes but reads as well. (page 2, end) If you do a monthly scrub you already have 216TB of reads so it can be safely assumed that a lot of customers blow well past these numbers. This limit is in use since the 2TB drive area and simply does not fit 9x larger drives. ServeTheHome talked about this years ago.

I will just paste my standard procedure when I onboard any new (or used) drive: Everybody has their own skin care HDD check routine. This is mine:

I first check the SMART status with CrystalDisk, after this a short smart test, full surface check with Macrorit, full h2testw run, CrystalDiskMark, and then I check with CrystalDisk once again if anything besides power on hours did change.

Will take some days for a large drive but in terms of work hours we talk about less than 5 minutes and it covers pretty much anything without being too excessive.

Once you write ~400TB or whatever it’s rated for on a consumer SSD it dies.

Not really. Tests and my experience show this is just a pure warranty number. Meaning the manufacturer guarantees that the drive will do at least this many writes without failing and it reaching it also voids your warranty. However, you can usually expect 2x as many writes, although 10x and more is also not unheard of.

HDDs can take a lot more writes before dying.

They are actually often not rated for a ton of reads and writes. But once again this is more of a warranty thing and HDDs are usually unmetered so…

I think there are other factors at play. The community here is much smaller and the few people that are here are likely more dedicated and knowledgeable.

Just get an 18-22TB external drive. Cheap easy and can be reused once you outgrow it. Yes, a NAS is pretty cool but unless you need the uptime etc RAID can offer you are just better of getting a single, large drive.