Definition of predating
The last known instance of two "bonuses" being used is March 26, 1996, which had Clue in Round 2 and a Place in Round 4 of NEW HAVEN CONNECTICUT (followed by Pat asking the contestant which Ivy League university is based there).
The decision to use no more than one per game may also be related to time constraints.
Neither has appeared after Round 3 since about 2002, except for a single Same Name used in Round 4 on September 13, 2004.
Introduced in Season 10, and definitely by October 26, 1992, these puzzles included things and events related to the decade in question.
Until the end of Season 13, such questions were indicated by four low-pitched beeps and asked by Charlie; after this, they also used the High Rollers chimes and were asked by Pat.
Such questions last appeared on May 23, 2005 with the Quotation I'LL GET YOU MY PRETTY AND YOUR LITTLE DOG TOO!
Occasionally, games have had two categories used twice; April 28, 1988 and March 17, 2003 are the only known games in which three categories (Phrase, Thing, and Person on the former; Fictional Characters, Thing, and Around the House on the latter) were used twice.
It is still fairly common for the Bonus Round category to be a category that is used in the main game.
Perhaps in relation to the above, many games before 1996 had more than one "bonus" category, and there are only two known instances of one being duplicated: Clue was used twice on both November 23, 1992 and March 29, 1995, the latter of which is notable for being the only known game composed entirely of "bonus" categories (the other two being Megaword and Fill In the Blank in Rounds 2 and 3, respectively).