Ah, sorry, I misunderstood this!
Our numbers go like this: Since about two months we run a three node PVE/Ceph cluster (so I guess that our writes on the system disks are higher than yours because of Ceph). We monitor disk IO and see a constant write flow between 250 and 450 kB/s, let's say, 350 kB/s on average. If my calculation is correct, than 1,4 PBW would give us a runtime of about 125 years.