I’m concerned about those drives. While they’re not under a lot of load, every drive will fail eventually.
Go into your storage manager in DSM and check the drive health.
You could always replace failing drives on the same NAS, but replacing the NAS just to replace it seems like a waste of money, unless your needs have changed.
Provided that you have a backup solution (a NAS isn’t a backup solution on its own), then you should be covered even if the drive(s) fail.
FWIW, I only use Seagate Ironwolf drives in my NAS.