Well, we're not in an El Nino yet. But in general, yes El Nino's tend to be shorter-lived than La Nina's due in part to what they represent. La Nina is an amplification of the existing climatological pattern in the Pacific while El Nino is the opposite. What makes El Nino go, also leads to its demise. 

You can learn more at  https://www.climate.gov/news-features/blogs/enso/life-and-death-el-ni%C…

As for ENSO and climate change, we have a bunch of articles on the topic.