Outsiders (and often manager types) might assume that programming work is consistent during the day, and programming "just happens" at a steady pace. There is a thing programmers refer to as "the zone", and it is when your entire energy is focussed on something. Nothing around you matters and you become totally engrossed on the issue at hand. This is not really something that can be controlled, and I don't think any programmer could constantly do this all day without burning out.

What "the zone" means is, over an 8 hour day, 50% of the work done that day, might be done in a single hour, with the other 50% spread over the remaining 7 hours. It's not laziness however, it's simply an alternative work ethic as opposed to working at a constant pace all day. Think of an olympic sprinter - they jog and train normally most of the day, and then have a period of fast sprints, which is what they have built up to over the day. You could not expect them to sprint all day, or you'd quickly destroy their passion and burn them out very quickly, much the same with programming, as it is mentally taxing after a period of time.

One of the most important things to realise is that this zone can very easily be interrupted, and it's hard to get back in it if you're distracted from what you're doing. As a programmer, it is better to be able to concentrate on a project solidly for a whole day and do a bunch of smaller maintenance jobs the next day, than be interrupted with small tasks constantly throughout the day which require a different mindset.

Anyway, just a small bit of insight I thought may be of interest to some people...