Lifespan of Synology NAS

[DavidL]

Another data point:
I got a DS412+ in 2013, with 4 x WD 4TB Red disks. 1 disk failed after several warnings in 2018, at 35000 hours. I replaced it with the same type WD 4TB Red. Now have 47000 hours on the clock, running 24/7. After the failure in 2013 I bought an additional WD 4TB Red disk so that I would be able to immediately replace any failed disk and hopefully avoid a situation with 2 failed disks. I'd recommend this course of action.
I'd agree with Simon that it is worth investing in a model with a more powerful cpu etc. The DS412+ has no problems with my current music streaming needs but I'll probably replace it with a more recent model which will support streaming of 1080p video rather than 720p that is the limit for the DS412+.