Keyword Limits

After trying to upload a new, tightly-themed campaign in Adwords Editor, I got this message:

"AdWords Editor is unable to check or post some of your changes, because doing so would cause you to exceed AdWords account limits..."

I have just over 15,000 keywords, which seems relatively small in comparison to some I've read about. Several reliable sources (including Jeremy, Amit Mehta, and the SpeedPPC training videos) suggest using misspellings, multiple matching variations and other ways to maximize keywords.

Google, on the other hand, states the following:

Don't ...

* Include these variations: misspellings (french cusine), capitalization (French cuisine), incorrect spacing (french cui sine), hyphens (french-cuisine).
* Use variations that are more than three words long (best for unique markets and product names).
* Use a three-word keyword in multiple matching variations at one time: [buy red bicycle], "buy red bicycle," buy red bicycle.

Do you compile massive keyword lists and then delete those with few or no impressions? And if so, how long do you wait before doing so? Or do you get around this limitation by creating a new account?

Thanks.