Almost always shorter is better. Hyphens or not, shorter is better...
Except when it falls into the Arnold Schwartzenegger category where remembering it means it becomes unforgettable.
Back to the hyphens, if a domain can have ALL hyphens, and has three full words (tested to 5) it will outperform the identical domainname without spaces.
If you have multiple letters the same, then hyphens become really effective
I think there is a readibility score based on letter proximity, but I go for the easier to read any day.
If everything has gone in your particualr area, add a short suffix word like tips, blog etc.
There are more advanced techniques but are way outside the scope of the Challenge
fillleveltips | fill-level-tips
filllevelblog | fill-level-blog