It depends on what you're doing. I've been doing Haskell full-time for the last five years and the vast majority of the time I haven't had to think about lazin

It depends on what you're doing. I've been doing Haskell full-time for the last five years and the vast majority of the time I haven't had to think about laziness. But there have been a handful of places where I did need to think about it. It's certainly possible that those situations will be much more common in some types of work. But I think if you average over the whole software industry you probably won't need to think about it very often.