Keep it in balance. It's a billboard. Offending Websites have no immediate ability to send someone an e-mail message or ask a question. This space is free. Stale Studies show that visitors rarely visit a non-changing site more than 3 times.
Fresh sites are simply more successful.
A good rule of thumb is that publishers and big companies should update their sites at least weekly. Smaller companies can sometimes go a month without updates. Even better, have a daily message, fact, quote or and info nugget to keep people coming back until your site becomes a regular stop for them. Also try to stay in contact with your visitors like sending them a like a daily, weekly, or monthly newsletter. Many Websites don't give the visitor a reason to return.