How Old is Too Old to be Relevant?

This is going to be a short post, but I just wanted to comment on my astonishment at how much info is out on the web about blogging. Most of it is posted on blogs...go figure. I've search "components of blogs", "how to start a blog", "blog tools", "how many blogs exist" and that's just a starting point. It's overwhelming and difficult to grasp was parts are really relevant.

Something that struck me though is how relevant and up-to-date with current trends can some of these posts be when many are a few years old. How old is now too old when it comes being relevant? I know the lady that works in the resource library in our facility does not keep any journals on the shelf that are more than a year old.

I can barely keep up with the constants streaming of information I receive daily through Twitter and these are just the select few people I have decided to follow. What about the thousands of others out there that are posting, tweeting, sharing their information, thoughts and ideas.

Is there a point in time that you don't reference back past? Do you give yourself a limit as to what you pay attention too? Is there a standard that we all should be following and if so does that mean the past is irrelevant? (I dare not ask that question).