There were 256 regular season games this season, and by my quick (and unofficial) count 11 of them went to OT. Also one OT game out of the 10 played thus far in the playoffs (NYJ/SD). I really have no idea if that # of OT contests for a season is high, low or about the norm, I don't have that data. So I'll assume it's somewhat normal.
So that's 12 games out of 266, or about 4.5% of the time. Factor in a higher percentage of games in the regular season which could be expected to be mismatches (as there is a wider gap between the best and worst teams in the regular season than in the playoffs), and maybe you could expect any given playoff game to go to OT about 7 or 8% of the time.
-900 actually looks about right to me. In other words, I would not risk it. In fact, if you were a believer in the "their due" line of thinking, you could make an argument that we are long overdue for a Superbowl OT game. Also keep in mind with the 2-point conversion ties are much more likely than in the past, which may account for part of the reason why there were no OT SB games in the early years.