If you have older blog posts that people still read, then it is best to update the information. Especially if this is a review site and things have changed about your review. You can always leave the article the same as it is and add an UPDATE to the article. In the update, you'll explain all the changes and what has happened since you wrote the post. This is very common in blogging and especially in review sites.
However, if you are writing how-to articles that tell a person how to do something and the technology has changed it is better to write a new article with the new instructions on it. Go back to your original article and write an update that will tell people that some of the steps have changed and let them know for what program. For example, if you wrote instructions for using Windows XP and now you need to tell people how it will work in Windows 7 or 10, you will add this to the update. You will also add a link in the update to go to the new set of instructions.