I wouldn't call them dull. You may be more prone to daydreaming than usual, or have more vivid dreams at night. There may be a sense of confusion about things or a lack of focus, but this aspect is a really good time to do creative work of any kind: the annoyance produced by the square can be used as fuel for more "right-brained" activities.
IMO the stars don't make anything happen, they simply reflect what is already occuring via synchronicity. By knowing when you're born, you can look ahead to see what part of the various cycles you're at in your life and get some idea of what to expect.
This aspect - as with any other - always depends on what other placements and aspects you have in your natal chart. A highly aspected Neptune would feel this transit more powerfully than someone who doesn't have many aspects to Neptune. Neptune being a slow mover is more generational than personal unless it's prominent in your natal chart.
This happens about twice a year (sometimes more if Mercury goes retrograde). You can see when it will happen for you again by going to astro.com and entering in your birth data. Under the free charts section, there's an option to draw up a natal chart with transits. Since Mercury goes retrograde about 3 times a year and I don't know the degree of your Neptune, I can't get more specific.