Well, the first J-20 made its first flight in January 2011.
All in all, since January 2011, the following aircraft have been introduced (I will include the first in the list too)
2001 - First flight January 2011
2002 - First flight May 2012
2011 - First flight March 2014
2012 - First flight July 2014
2014 - First flight November 2014
2015 - First flight December 2014
So, now, four years and there months after the first flight, the PLAAF has flown six aircraft. They took a year and four months to introduce the second aircraft, and then another two years and ten months after that to introduce the 3rd.
Since that time, in the space of nine months, they introduced three more.
This is indicative of the PLAAF being fairly happy with the state of the aircraft and producing quite a few for more detailed testing.
I'd say they are not going too fast at all.
I would expect the aircraft to go into LRIP (if it is not already) within the year, and then reach IOC perhaps as early as 2018 as one poster already predicted.. That would be seven years after the first prototype flew and for an aircraft like this I would not consider it too fast at all.
Aggressive? Perhaps. But certainly well within the capability of a nation like China and their form of government which is not as impacted in terms of their development and production by all of the various constraints a nation like the US places on itself.
Even with those constraints, the US took the F-22 Raptor from first flight in September 1997 to initial service in December 2005...just over eight years.
So you see what I mean.
