Being up-to-date  in world is hard. You really need to study and try new things every day.
I remember early days of Spring framework, one of my friends asked me if is it necessary to learn  this new framework and I told him no. We both now are working with spring but we learned it when we have to.
I believe that learning new things must be on need, if you need it or if you are asked for it, study, try, do your job and then rinse and repeat.Â
Reading news sites like TSS, infoq and so forth is good and bad. Good for being informed of new things happening in the world and bad because it shows a lot things to study and learn and this will scares many people (like me).Â
I want to ask you something: Do you know which web framework has more usage these days? Seam, JSF, EJB 3, Spring, ...? Guess what. Struts 1.2! Yes this a 8-years-old framework.
Finally, IMHO just remember the names and a one-paragraph-description of new things. If someday you need to know more, do it.