Longest Gap Between Characters

[Kahran Ramsus]

David Hedison was 16 years as Felix Leiter between Live and Let Die and Licence to Kill.
Karen Allen was 27 years as Marian Ravenwood between Raiders of the Lost Ark and Indiana Jones and the Kingdom of the Crystal Skull.
David Niven was 19 years as The Phantom/Sir Charles Litton between The Pink Panther and Trail of the Pink Panther. The character was played by Christopher Plummer in between Niven's performances.

 

[WorthyStevens]

Johnny Depp - Tom Hanson - 21 Jump Street (21 year gap)

Technically.

 

[3rdstone]

Kurt Russell as Snake Plissken - 15 years (Escape From New York -81, Escape From L.A -96)

 

[DarkKnight88]

Mark Hamill, Harrison Ford, Carrie Fisher as Luke Skywalker, Han Solo, Princess Leia - 32 years (Return of the Jedi 1983 - The Force Awakens 2015)

B.D. Wong as Henry Wu - 22 years (Jurassic Park 1993 - Jurassic World 2015)

Jeff Daniels and Jim Carrey as Harry and Lloyd - 20 years (Dumb & Dumber 1994 - Dumber & Dumber To 2014)

Jeff Goldblum and Bill Pullman as David Levinson and President Whitmore - 20 years (Independence Day 1996 - Independence Day 2 2016)

Ben Stiller and Owen Wilson as Derek Zoolander and Hansel - 15 years (Zoolander 2001 - Zoolander 2 2016)

Albert Brooks and Ellen DeGeneres as Marlin and Dory - 13 years (Finding Nemo 2003 - Finding Dory 2016)

Marlon Brando as Jor-El - 28 years (Superman 1978 - Superman Returns 2006) … technically

 

[TheDreamMaster]

Don't know if anyone has mentioned, but the Star Wars cast that didn't return, (i.e. Peter Mayhew and Anthony Daniels were in Episode III in 2005) now all have a gap from 1983-2015, a total of 32 years.