I like the ideas of getting up early to do work, I might try that. I'm usually either really tired afterwork so just chill out then sleep, or I'm pumped up and work until the wee hours of the morning.

Also don't underestimate how much time you can scratch on the job. I carry a A4-size book around and jot down ideas, think through problems etc when we're waiting for other people to get to a meeting or some other hold up. It all adds up and saves being bored.