@ithoughtisawa2 That's a good hint. Thanks.
No problems so far, but I wasn't aware it was running so long already. SMART looks okay. Maybe this HDD will still last some time. But at those prices and how they just get higher and higher, it'll probably be wise to buy something and anticipate the failure.
Re data protection: my server runs Unraid and this HDD is the parity drive. So no problem. Same, if it would be one of the data drives.
With this setup I could even use the new drive already as second parity drive and just increase the level of fault tolerance.