The stark realization is that the longer you live, the faster time will appear. Since we don't know how long we live, this process accelerates faster than we can perceive it, until eventually we can no longer can observe time.
Time is fairly cut and dry, it's very linear. The interesting bit I find, isn't so much time, but rather experiences. We trade time to gain experiences (good or bad). It's a finite currency, but experiences can saturate, and thusly distort the feeling of time further. Doing a mundane task can feel like an eternity, but learning something new can cause time to fly by. I wonder if it's your subconscious realizing that have spent X% of time doing a task and is sending you signals to do something new. I know for me, it's impossible for me to do nothing. With a lack of external stimuli, my mind wonders and I day dream; which, I suppose, is still an experience since no two thoughts can be alike, just as any two moments in time.