+1!Yep, the likelihood of one of those drives failing is pretty low as it doesn't get accessed as much. Besides the extra cost of the drives I think the only downsides are more power consumption and a little more heat into you computer. Not that big of a deal.
I guess we can say, separate drives are better, but more expensive. A single partitioned drive is a good, less expensive alternative if keeping your data intact is important to you.