Here's how I see the timeline ...
- November 8, 1983 -- Thomas Wayne murdered. Bruce is 8. (Date from some casefile or something).
- 1996 -- Joe Chill paroled. Bruce expelled from Princeton and leaves Gotham. He is 21.
- 1996-2003 -- Seven year absence from Gotham. Training.
- 2003 -- Bruce returns to Gotham at 28yo. R&D for Batman. Batman's first night.
- 2005 -- League of Shadows attack on Gotham on Bruce's 30th birthday. There is about 2-years between Bruce's return and the LOS attack.
- 2005-2008 -- three year off-screen war on crime;
- 2008 -- events of The Dark Knight occur. New Batsuit. Bruce is 33;
- 2008 -- last confirmed sighting of Batman after Dent's death;
- 2008-2016 -- eight year gap between confirmed sightings;
- 2016 -- Events of The Dark Knight Rises, Bruce is 41.
To support the three-year gap between Begins/TDK.
- Jim Gordon's son is 2-years-old in Begins. He's clearly older than 3 in TDK. At least 6.
- The Dark Knight manual references that Batman used the Begins suit for 5-years. 2003-2008. First night through TDK's new Batsuit.
- A gap between Begins and TDK explains why the Joker has a reputation with the mobsters and his bank robbery accomplices.
- The gap between Batman's first night and the LOS attack also allows time for Ras al Ghul to exile Bane before his death.
That would mean Bruce was Batman for 5-years ... 2003-2005 (Begins); 2005-2008 (b/w Begins and TDK); 2016 (TDKR). I also like the idea of unconfirmed Batman sightings in 2009 and 2010, before Bruce's injury and official retirement. So, you might be able to stretch it to 6-years.
Originally Posted by The Joker
Joker: "A year ago these Cops and lawyers wouldn't dare cross any of you"
This may not reference a year since Batman's initial appearance. Just one year since Batman is having enough impact to scare them into daylight meetings.