hard drive - Is it better to have HDDs on standby after a while or not for a 24/7 home office server?

I have a NAS with a WD Server HDD (3 years old, 1TB).

Is it better to have it running all the time, or should I put on the standby time to make the HDD shut down after a while?

It comes out of standby about 10 - 20 times a day, and it makes that weird noise when it wakes up. It did it from day 1 on so I guess its normal.