I got the same setup with eight 18TB Exos drives running in a RAIDz2 with an extra spare. Added to this though I got another vdev of eight 12 WD reds with another spare.
With this I can have 2 drives fail in a vdev at any point and still rebuild the pool. Though if more than 2 drives all fail at the same time the whole pool is gone.
But if that happens I have a second NAS offsite at my bro's place that I backup specific datasets. This is connected with tailscale and a zfs replication task.