Hard disks can break and accidents can happen.

I like to be safe. I keep my images on three external hard drives, and one of them is always in a different location than the other two. Plus I do cloud backup for my work, plus the most important material.

Backup, backup, backup at least weekly if not daily.

I find small hard drives (min 2TB max 4TB) easy to use and replace, Toshiba being my preferred brand.

I'd agree. Even thought I got a fantastic deal on the 8T I still use smaller drives, by content, like music on one, video on another, GoPro on another, racing on... OK you get it. The massive drive is the backup of the backups.

And like bestravelvideo, kind of, I buy a new external drive every year and every couple years I put the old drives on the book shelf. Drive prices keep coming down, they are faster and more reliable, but I keep the old ones, just in case. One (or maybe more) have all my floppy disks backed up. Remember floppy disks?  I suspect the hundreds of floppies I backed up, will never be needed, but what the heck, just in case?

No matter how people do this, three is a lucky number?  Anything less could be a problem, and anything more is better.

Don't let us forget RAID drives and bays?

Hi.

I have some storage problems (and have seen that increase mi pc hard drives again and again is not a good option). Could you recommend me external hard drives for stock? I'm thinking in 6 TB and several years of use. This is important to me, my external units have worked for years and intense use with no problems (seagate and iomega, about ten years and hard work -one have started to make some noise) but I need a better one as my main drive and would keep the others as backup. I don't want a very expensive one, if possible.

Thank you.

You can also consider use a RAID set up, although it's not a backup solution it can give more peace of mind. I use RAID 5 for store my footage (4 disks of 4TB) which allows 2 disks to fail and sill can recover all the information. I thing RAID 1 is more suitable for your because you only need 2 disk to do this, if one disk fails you can still recover all the information. In your case I will go for two discs of 6TB since You'll sacrifice half the capacity of the sum of the two disks.
I use the brand cineraid for the enclosure (hardware raid).
Hope this help