According to WaPo, there's a memo going around from the AP managing editor indicating new guidelines for story lengths:

Most daily, bylined digest stories: 300-500 words
The top 1-2 stories in each state: 500-700 words
The very top global stories of the day, at or near the top of the the digest: 700+ (but still tightly written and edited)

Why? Because "readers do not have the attention span for most long stories and are in fact turned off when they are too long."

I wonder if this is an effect of moving to largely digital formats? I know I can't be arsed to read anything on a screen much longer than a page or two (unless I'm the one working on it).