An hour seems like 5 minutes in studio time and in general as I get older.
Time is flying so fast sometimes!
I watched a NOVA documentary recently about time. One thing that stuck with me was the idea that time being relative, appears to the observer to move at roughly the square root of your age. We can observe this time and time again (no pun intended) by talking to the very young and the very old. When you are a child, time seems to move very slowly and we feel we will "never" reach driving age, for example. When we reach our later years, we seem to need less sleep because time seems to fly by, and our internal body clock is running much much faster.
I am 37 and I too have noticed how fast time seems to be going by, especially in the studio where I am hyper-focused on any given task.
Be careful not to listen to Pink Floyd's "Time". It will thoroughly depress you at a time like this.
One reason, it seems to me, that time seems to flow much more slowly to the young is that there are many more unique 'anchor points' for them. Much more of life is new, so there are many more unique or first time(s) experiences happening to them, so there are a lot more things in a given period of time that serve as anchors against which they measure the passage of time.
As you get older, no matter how much you try to mix it up, much more of life is the same as it was yesterday. There's less and less that stands out in order to serve as an anchor to provide perspective backwards in time, and fewer unique events in a given day to give them them depth and fullness.