I freelance for the local paper and we've been told to keep our stories about 700 words - much more than that and you lose readers. Reading online is a lot different than writing for print.
Admittedly, a couple of my hubs are long (1,000+) but I try to keep them around 700-800 words. If you go for long, make sure it's broken up with subheads, pictures, etc. That helps readers. But regardless of length, if it's well-written with good info, people will read it to the end.