Bob Costas and Tim McCarver will almost certainly set a "record" tonight when they call the Padres-Cardinals game on MLB Network. As best as I can tell, this will mark the longest gap between games on national TV networks for the same announcer team at 33 seasons. This duo last worked together in 1982 (see note below).
So which team holds the standard they are about to break? According to my research, that would be the 25 season gap for Jim Nantz and Bill Raftery on college basketball. CBS paired them in 2015 on the #1 crew after they had last called a game together in 1990.
Here are the longest such gaps that I found (while looking at MLB, NFL, NBA, CBB, and CFB on national TV networks):
33: Bob Costas, Tim McCarver 1982 (NBC) - 2015 (MLBN)
Note: A recent MLBN press release claims that Bob and Tim last worked together in 1980 calling two games on NBC that season. However the SABR network TV database (which is based on the historical announcer research at 506sports.com) credits Costas and McCarver with working one game in 1980 and one in 1982. For the purposes of this post, I am trusting the info from SABR/506sports and suspect that the MLBN press release is incorrect.
25: Jim Nantz, Bill Raftery 1989-90 (CBS) - 2014-15 (CBS)
This gap is even more remarkable when you consider that both Nantz and Raftery worked for CBS during the entire time period.
23: Jim Simpson, Bill Raftery 1981-82 (ESPN) - 2004-05 (ESPNCL)
In 2005, ESPN Classic aired a series of Turn Back the Clock games with vintage graphics and brought back Jim Simpson (who had been a mainstay in the early ESPN years) to call the games. As far as I know, the last time Simpson worked with Raftery was this 1982 Big East matchup (although I don't have complete ESPN announcer listings for the 1980s).
19: Dick Enberg, Billy Packer, Al McGuire 1980-81 (NBC) - 1999-00 (CBS)
This is the longest gap I found for an announcer trio. After working on NBC through the 1981 NCAA Tournament, 19 seasons elapsed before CBS put them in the booth for a reunion game in 2000. Of course, Enberg and McGuire called many games as a duo during this gap.
17: Bob Costas, Bob Uecker 1997 (NBC) - 2014 (MLBN)
MLBN has added intrigue to its telecasts in recent seasons by using some old-school broadcasters. Bob Uecker had last worked with Costas during the 1997 postseason.
15: Dick Stockton, Matt Millen 2000 (Fox) - 2015 (Fox)
13: Curt Gowdy, Al DeRogatis 1975 (NBC) - 1988 (NBC)
10: Curt Gowdy, Merlin Olsen 1978 (NBC) - 1988 (NBC)
<UPDATE 1/22/2016 - Added the Stockon-Millen gap.>
Dick Stockon and Matt Millen were reunited in the Fox NFL booth for a 2015 game after having last worked together on a playoff game after the 2000 season.
During the 1988 Summer Olympics, NBC brought back some legendary announcers to fill in on September and October NFL games while much of its regular talent roster was at the Seoul games. This reunited Curt Gowdy and Al DeRogatis for a few games 13 seasons after they last worked together which was the longest NFL gap I found.
Note: This is not the easiest topic to research, so if you know of any announcer team gaps spanning at least 10 seasons which are missing from this list, please let me know.