One of my drives was at 7 reallocated sectors for about a year. I acknowledged the error and kept using the drive as normal. Within the last month, the error count grew to 132 and then 164. At that point, I stopped all write operations to the array and began migrating data out of that drive using unbalance. During the migration, the error count grew once more to 1440. There is 1TB of data left to move, and the parity is protecting me. I'm going to replace this drive.
In another server, my parity drive now has 24 reallocated sectors. This one is a bit trickier to replace because my data will not be redundant while parity rebuilds. I will report back here in the future with what I experienced as the drives failed. I have never seen a drive fail before, so I want to take these ones to the end.