How often do we get repeat matchups in major bowl games? I'm including the following:
BCS Era - National Championship, Fiesta Bowl, Orange Bowl, Rose Bowl, Sugar Bowl
CFP Era - Cotton Bowl, Fiesta Bowl, Orange Bowl, Peach Bowl, Rose Bowl, Sugar Bowl (note: the CFP National Championship is not a bowl, is not selected by a committee or polling, and does not qualify for this thread)

We have major bowls with formulaic matchups which predetermine what conferences can send schools to those bowl games in certain years like the Orange Bowl, Rose Bowl, and Sugar Bowl. Regardless, these are included. I presumed that these formulaic bowls would produce many repeated matchups. I thought there would be plenty of the same matchups because we see so many of the same names at the top of polls every season.

Let's get down to the stats for the 132 applicable major bowl games:

Only 12 matchups were repeated and only 1 of those 12 matchups occurred more than twice (26/132 matchups = 19.7%):

4X
Clemson vs Ohio St

2X
Alabama vs Michigan
Alabama vs Notre Dame
Alabama vs Oklahoma
Florida vs Oklahoma
Florida St vs Georgia
LSU vs Oklahoma
Michigan vs USC
Notre Dame vs Ohio St
Oregon vs Wisconsin
Penn St vs USC
Stanford vs Wisconsin

The remaining 106 matchups (80.3%) were unique.

After reviewing all of this, it makes me wonder of powers-that-be try to avoid rematches of major bowls when possible.