I actually use Microsoft's SyncToy to sync 2 hard drives so that Hard drive 2 is the mirror of Hard drive 1, as a back up, and so that both are independent and even when one goes bad, a totally independent one can work.
But say if I don't sync to 2 weeks, and now drive 1 has 60GB of new stuff (or more), and copying may take 1 hour or more. In this case, will it stress out either drive when I do a copy finally? In general, how long of continuous copying will stress out a read drive and a write drive? (I just hope SyncToy has an option to "copy 1 file and rest for 1 minute for any file greater than 500MB).
(these are WD 3TB Element drives)