Just don't forget that IO matters. Drives do 140-220MB/s depending on the LBA distance of the readhead, and that's not really changing. 160MB/s is very common.

Just don't forget that IO matters. Drives do 140-220MB/s depending on the LBA distance of the readhead, and that's not really changing. 160MB/s is very common. So your 8TB drives, assuming 1MiB writes with a 20ms latency and 160MB/s, you can rewrite the drive ~155 times/year. At 20T this drops to ~62 times/yr.