This would be fun for when LEOs come in to take your computer, they can easily keep it powered so all of the decrypted keys stay in memory. Killing power means going back to an encrypted state. In high profile cases for desktops, there's techniques for splicing the power cable to switch to a battery pack. This would make it much easier for the unskilled LEO to take your shit. Cause we all know you're the one their after. Sleep tight! ;-)