In fact we were told recently at my company to keep every ppt deck under 4 pages if we can. No one has the time to read long presentations.
It's no fun to exhaust my audience.
If you're trying to pitch someone on why your redundant project shouldn't be canned then you should probably keep the slides simple and to the point and add in any extra stuff you need in the delivery of the presentation.
Write a 1-page brief. Make a tabloid-sized poster. Write a blog post. Save your bullet list in a plain text file somewhere. Scribble the main ideas on a chalkboard. Slide decks are the worst possible medium for use outside the context of a presentation (heck, they are a pretty terrible medium even for that context).
But over time people feel the need to stuff more things in them and you end up with 40 slides decks that defeat the purpose.