Do you also do the same thing every time a new kernel ends up in your /usr/portage? Here's a Ruby script that does all required steps automatically for you:

• The kernel symlink gets updated to point to the latest kernel in /usr/src/.
• An existing .config file gets copied from the previously used kernel.
• genkernel is used to compile the new kernel.
• The kernel gets installed on your /boot partition.
• /boot/grub/grub.conf gets updated (please check manually before booting) to use the new kernel.

Here is a Ruby script that uses sg3_utils to automatically put a SCSI device into standby mode after a configurable idle time period. This also works with USB storage devices (tested with Linux Kernel 2.6.14, sg3_utils 1.11 on Gentoo Linux with an NEC PCI USB 2.0 controller and an external Samsung SP2514N hard disk in an ICY Box).

You can download version 0.1 here.