Russ,
I suppose it depends on how you envisage someone's life-schedule. For some people, knowing they've got 20-chapters and they've only read 5, they can think "It's okay, got 15 more left... I don't need to get it yet..." (then something happens).
There's a lot of scenarios that could come up, the above was what I was thinking of as opposed to the reader losing interest (in which case that's something else to worry about

).
I'll go over to the writer's corner - thanks for the tip.
Regards,
Paul.