Also whatever you do, don't buy all one kind of disk. That'll be the thing that dies first and most frequently. Buy from different manufacturers and through different vendors to try and get disks from at least a few different batches. That way you don't get hit by some batch of parts being out of spec by 5% instead of 2% and them all failing within a year, all at the same time.
If you do somehow manage to pick the perfect disk sure having everything from a single batch would be the best since that'll ensure you have the longest MTBF. But how sure are you that you'll be picking the perfect batch simply by blind luck?
As long as you're not buying all the disks at once sticking with one manufacturer and brand should be fine. If you're buying 25% of your total inventory every year it'll all be spread out to just a few percent per month.
But when you're buying 100% of your disk inventory at once there's a serious "all eggs in one basket" risk.
If you do somehow manage to pick the perfect disk sure having everything from a single batch would be the best since that'll ensure you have the longest MTBF. But how sure are you that you'll be picking the perfect batch simply by blind luck?