It’s an obligation for a blogger to always updates his blog, like a journalist who always writes a new article for the newspaper. But sometimes a blogger doesn’t live only for blog update every time, or even if lacked inspiration.
Within the empty condition or blog without update like this, better performing republish an old article. But the type of article to be posted is the type of article that doesn’t depend on time, which mean past, present, or tomorrow, what has written in the article can still be useful for anytime. For examples: article about tips, recipes, lesson, poetry, song lyrics or knowledge. Whereas article such as news, events or things that change, should not be posted anymore because it will be something stale.
In this way the search engines will think that you are updating your blog and your blog looks fresh again. One more thing you have to do is setting your permalink(you should do this at first time before you make posts or when you start to blog).
Your blog url before:
This way to avoid duplicate content of url on blog that has been indexed on search engine previously. For wordpress user with selfhosted better using Seo Search Tagging plugin because it can be tuned for auto repost or you can use Old Post Promoter plugin, old post spinner, or repost.us.