Blogger accounts and Blog*Spot addresses do not expire.
That's good news - if you're the blog owner. Short of your blog being hacked, what you publish will remain online forever. Of course, your ability to maintain your blog and URL will be subject to your ability to maintain the account that administers the blog. And the future online status of the blog will be subject to how it's published, and its future after you're gone.
That's bad news - if you're the wanna be publisher to the URL, and that URL is not available. Neither current blog content, nor publishing activity, is relevant to URL availability.
Periodically, we see the question
I want to publish my blog to this URL. There's a blog at that address, but it hasn't been updated in years. Can Blogger give me that address?And the answer is, of course
No. See the Blogger Help postBlogger accounts and Blog*Spot addresses do not expire. Therefore, we can't take away somebody's blog address to give to you.
And, inevitably, the next question
Can Blogger help me contact the owner?and that answer is
No. If you see an email address on the blog, use it.
The email address, for many Bloggers, is half of the authentication, to the account used for maintaining the blogs. Would you want Blogger giving out your email address to anybody who asked for it? Nope. So would you expect Blogger to give you somebody else's email address? You may, at your own discretion, publish your blog anonymously - and the other guy has the same option.
If you are setting up a new blog, pick an available URL, and get started, today. Don't waste your time, and other people's time, wishing for a URL that you want but can never have.