I think the right way to think about this is: it is raised awareness (both self awareness and dream awareness) that results in lucidity in dreams. Lucidity in dreams is a sign that your LD practice is "catching on" in your mind. It is continued effort in progressing in the fundamentals that results in more frequent lucid dreams. Some kind of effort I think is always required. But the more you get lucid, the more your mind gets used to operating in that mode, the less effort it takes to sustain a particular level of lucidity (either frequency of dreams or the level of lucidity). To reach ever higher heights, continued effort is certainly required. It's like any discipline that way.