Notes spacing

[Raphael Slinckx]

Hi !

I have a problem with notes horizontal spacing, I want the score to be 
less cluttered, so here is my \paper block

\paper {
   \context  {
      \ScoreContext
         \override SpacingSpanner #'spacing-increment = #5.0
   }
   #(set-paper-size "a4")
}

As written in the docs, it works but only for the beginning of the song, 
then after 10 measures (and maybe a page break), the notes are cluttered 
again !

Is there something that break the spacing command ? Or does it applies 
only to the first page ? Can other "tweaks" affect this setting ?

Many thanks !
Raf