Basically I'm looking for a drive solution that will last me 5+ years at least without worrying about it conking out at any point.

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You never really been able to count on a brand new drive manufactured in whatever current year lasting 5+ years.

Buy two drives, install the OS on both, put one in a safe place and back up regularly!

Setting up an extra SCA drive in an external case with bootable partitions for all your OS choices for all your Macs is probably your best bet.