Writes Diana near forever, as far as I know but, it should be booted down every 10 to keep the memory from bleeding.
I have two of them.
I have a copy of my data backed up on two external hard drives . . . yes, I had one fail and lost everything - so now I use a system of replication. If one fails, chances are the other one isn’t going to fail at the same time - just out the money for a Seagate, unless you buy it at Costco where you can just go and trade it for another one and then reback-up the data!