Question regarding batch downloading

[PerseusRex]

So I'm just curious, I've tried this on two external hard drives and they end up with reallocated sector counts early into it's life. Does downloading too much do something to the hard drive in some way?

[L4cache]

Downloading (writing) tons of data surely does something to the hard drive, but usually not this kind. They are not like SSD-s.
Some bad or low quality sectors may already exist when it produced, out of unluckiness, or occur because of vibration/shock during operation. Because it's a external hard drive, the quality control can be not as good, and chances for vibration/shock will also be increased.
You can continue to use it if there's only a few numbers and not increasing. But remember to backup important files.

[L4cache]

This issue is totally off topic though