I work set hours and days, and occasionally throw in an extra day or stay on later if desired. I like to work that way! Although, my personal life doesn't really allow for "fluid" work days - I have set days where I CAN work, so I do.
I generally always work at my advertised times too, after always slacking off early and not being consistent when I first started. Although, if I am due to start at 10am, but don't have anything scheduled til say midday, and there is little chance of me filling that time at late notice, then I'll take my sweet time in getting to my work place. 9/10 times I wont have missed any bookings by doing so. This morning, however, I didn't have anything scheduled til 11am, reg texted at 9am trying to book 30 mins at 10am. I had fully intended on swinging by the coffee place for my fix then slowly sauntering in. Instead, I threw myself into my car and drove the 40 mins to my flat, buzzed that I had got the time filled :-P
Again, with booking requests for nearer my finishing time, I will accept and honour them. I never used to, but I have become wise in my experience and now know that even one extra booking is better than cutting my day short then kicking myself for losing work out of sheer impatience or laziness. I now use any inbetween time to work on other stuff. Sometimes I go for a nap.