Having just done my first week back at work after a week and a half off, I've noticed that the time seemed to pass at different speeds each time.
Luckily, the time off seemed to last and the time working went fairly quickly. I don't usually notice it as the weekends seem to go at the same speed (or at least my perception of it), so its only really apparent when I have longer off. The only time I really notice the working week has gone fast is when its seeming suddenly got to Friday. Long term, it doesn't seem as though I've been working for as long as I have since finishing my masters (which, granted, has been less than a year, but it doesn't seem like anywhere near it).
As said, this is just my perception of the time passing. Maybe the seemingly quicker weeks is because my sleeping pattern has changed from late nights and sleep ins when I was a student to early mornings for work.
Part of me thinks I should be more productive in my spare time, albeit the small amount of it that I have, but the problem then comes of not being able to think of anything productive I can be doing for a few hours after work with less energy than I'd like as I've been at work all day. Think I'll just stick with relaxing in my spare time for the time being, seems to be working for me for the moment :)