I don't particularly like the Seagate FreeAgent line of drives. Ever since I tried the first one - a 500GB specimen - and it died on me while still connected to a machine running CentOS. One moment it was fine, the next it was gone or remounted read-only. I figured out it happened whenever the drive went idle. I've stayed away from them ever since.
Lately, however, I had to work with a FreeAgent drive again and this time I found this solution to the problem by trolav that uses the power of udev and sysfs to keep the drive working whether or not it's idle. While the solution is posted on an Ubuntu forum, it works well on CentOS 5 as well.