The ear demands variety, whether you are reading aloud or not. Varying your sentence lengths creates a pleasing rhythm for your reader.
Just like songwriting is about more than lyrics, writing is about more than words. It's about rhythm, too.
So whether you're writing a PR pitch, press release, website copy or a marketing email, always remember to vary your sentence lengths.
The Hemingway App can help you identify issues with sentence lengths.
Source: Gary Provost