S.M.A.R.T. has been a lifesaver for me. It has helped me catch corruptions very early and avoid any catastrophes. Google published a study a few years ago claiming S.M.A.R.T. isn't a great predictor of imminent hard drive failure, but it sure seems to improve your odds of catching a problem early. I check it religiously on my hard drives.
I hope your other green drive is OK and boots up at proper speed!