In my experience it's not so much about missing deadlines with impunity, as negotiating up front what you're willing to commit to delivering. A lot of times you can put off some "nice to have" features without anyone complaining, as long as the core functionality is ready on time. (That may be what you meant by "delaying.")
The other part is renegotiating timelines when they make changes to stuff you've already built.
Financial security helps but the real key is being skilled enough to accomplish a lot without breaking a sweat. As much as possible, build reusable components with nice APIs, even if it means putting in some extra time up front. Always think about how to make your own job easier down the road, and after a while you'll have an easy job.
The other part is renegotiating timelines when they make changes to stuff you've already built.
Financial security helps but the real key is being skilled enough to accomplish a lot without breaking a sweat. As much as possible, build reusable components with nice APIs, even if it means putting in some extra time up front. Always think about how to make your own job easier down the road, and after a while you'll have an easy job.