The Interest object interestLifetime is seconds, not milliseconds.
diff --git a/js/NDN.js b/js/NDN.js
index 479ed30..f0267c5 100644
--- a/js/NDN.js
+++ b/js/NDN.js
@@ -68,7 +68,7 @@
 		interest.interestLifetime = template.interestLifetime;
     }
     else
-        interest.interestLifetime = 4200;   // default interest timeout value
+        interest.interestLifetime = 4.0;   // default interest timeout value in seconds.
     
     this.transport.expressInterest(this, interest, closure);
 };