When asked, "Mr. Lincoln, how long do you think a man's legs should be?" Lincoln replied, "Long enough to reach the ground."

So how long should a Blog title be?

Long enough to hit your objective. Some will disagree with me here.

Most SEO experts argued that the Blog title length must NOT be longer than 65 or 68 characters, and should be between 4 to 7 words.

Google shows 69 characters for blog title length.

Yahoo shows up to 72 characters blog title length.

Bing shows 65 characters for a blog title length.

Ask shows 69 characters for a blog title length.

Take a look at this sample from Amazon. It is on page #1 on Google.

Amazon.com: Fire Down Below: Steven Seagal, Kris Kristofferson, Marg Helgenberger, Stephen Lang, Brad Hunt, Harry Dean Stanton, Levon Helm, Mark Collie, Alex Harvey, Ed Bruce, Amelia Neighbors, Richard Masur, Jeb Stuart, Julius R. Nasso, Ronald G. Smith, William S. Gilmore, Philip Morton: Movies & TV"
The Blog title length should be filled with keywords that are relevant to your post.

Just because it is not shown does not mean that you can't have more characters.

Do your own homework to determine your blog title length.

Don't always listen to the so called SEO experts.

In closing I feel that you will NOT get penalized by Google for the length of your title as long as Google thinks it's relevant.