Line breaking every x bars

[Christopher Culver]

I've played at the top of \score{... the example in the manual for
line breaking every x beats so that I could have Lilypond place no
more than 7 bars on each page of my orchestral score, but when I run
Lilypond, it complains that it cannot provide such line breaking
because of "constraints". The resulting PDF has the staves going over
the right end of the page because it can't break onto the next page.

Is there another way I could enable such breaking?