A handful of years ago, perhaps when they went from 6 divisions to 8 divisions / 32 teams, the NFL instituted an "even-up" practice for the cross-conference (inter-conference) opponents. Given that the cross-conference opponents were only played once every 4 years, I think if a team went >8 years (2 cycles) not visiting an opponent's stadium they would "force" it on the 3rd cycle / 12th year, because they were going from a 3-year rotation to a 4-year rotation. The argument was the fans would get to see the opponent in their uniforms.
Given the more frequent intra-conference matchups, I don't think that policy applies within conference.
Lastly, I think when that divisional re-alignment occurred, the Bills had one or both of the Vikings and Packers games switched from road games to Orchard Park, because of that "rule". IIRC, neither team had visited BUF in a long time.
Re-writing this because this got super meandering the first time I tried.
There is no "even-up" rule, the cycle is set to 8 years with every team visiting every non-conference opponent once.
Year 1 (2002, 2010, 2018, 2026, etc) is in Buf's case at MIN, at GB, home for DET and CHI
Year 2 (2003, 2011, 2019, 2027, etc) is in Buf's case at Dal, at NYG, home for PHI, WSH
Year 3 (2004, 2012, 2020, 2028, etc) is in Buf's case at Sea, at SF, home for Rams, ARI
Year 4 (2005, 2013, 2021, 2029, etc) is in Buf's case at TB, at NO, home for CAR, ATL
Year 5 (2006, 2014, 2022, 2030, etc) is in Buf's case at DET, at CHI, vs MIN, vs GB
Year 6 (2007, 2015, 2023, 2031, etc) is in Buf's case at PHI, at WSH, vs DAL, vs NYG
Year 7 (2008, 2016, 2024, 2032, etc) is in Buf's case at Rams, at ARI, vs SEA, vs SF
Year 8 (2009, 2017, 2025, 2033, etc) is in Buf's case at CAR, at ATL, vs TB and vs NO
This will continue until there's expansion/realignment, at which point they'll have to re-jigger the schedule making process as well. It's also the same way with the full division crossovers inside your own conference. So in 6 years (one less division to cycle) we will host Pittsburgh and Cleveland and go to Baltimore and Cincinnati. It's the "one-offs" that are the reason we've visited KC so much recently. We also hosted them 3 times in a row in the reg. season between 2012 and 2014 (the 2014 ame being the home game in the 6 year cycle, the other two being one-offs)
That rule
may have existed when there were 6 divisions, because who you played from the other conference was decided by the previous season's records and not a set cycle (each divison had 5 teams and you only played 4 teams from the other conference, so you couldn't play everyone), but I'm not sure. I do know that no such rule has existed in 20+ years though.
There's an extra NFC game now that should rotate every 4 years (IE in 2021 AFC East teams hosted the NFC East team that finished in the same place as they did in the standings the previous year, and in 4 years they should be the visitors, although no information on that has actually been released past the first 4 year cycle of that particular piece of the schedule (you'll notice no NFC East team is listed for 2025
here).
