When seeking information on a topic, you should consider how old is the information. New knowledge is developed all the time. It is useful to examine the latest ideas, discoveries, and evidence available on a topic.
How old is too old? That can vary by topic. For some topics, new information discoveries may have occur almost daily. For example, a current event may have new evidence and information trickling in constantly. On other topics the defining ideas may have been developed years ago. Much of the evidence surrounding some historical topics was accumulated long ago.
In addition, some information is not available right away. For example, it takes time to collect health data about the country and then run statistics on it to find out what is the state of the health of the nation right now. So we usually have to settle for last year's data as "good enough" for now.
So it depends upon what YOU NEED for YOUR topic. And it also depends upon what is AVAILABLE for YOUR topic. The more you learn about your topic, the better you can evaluate whether you have included the most recent evidence and information. At the beginning, it can help to ask your professor or to see what your sources are saying about the currency of information on the topic.
