Is it better to have a disk drive run continuously or to have it sleep and start at least 5 times a day?

i'm switching from a big Windows PC with a number of hard drives in the box to a small MacBook Pro. I want to put all hard drives in USB docks.

It seems to works well but i have now some hard drives that go to sleep quite frequently.

In the PC which was never shut down, the drives were running constantly. I had set them to never got to sleep. Some of them have more than 3 years of running time but less than 50 start-stop cycles. I liked that.

Now it seems that i will have a smaller running time (because i will shut them down at night) but more, many more, start-stop cycles.

What is better for the life of the hard drives ?
I always believed that they could live longer with less start-stop cycles. Is it true ? are there any studies about that ?

Thanks