After a bit of research, here are some numbers for you to look at.
From 1949 to 1960, the NFL played a 12 game schedule. From 1961 to 1977, the NFL played a 14 game schedule. From 1978 to the present, the NFL has played a 16 game schedule.
Notable years, broken down by Rushing/Game:
1) OJ Simpson 1973 2003 yards 143.07 pg
2) Jim Brown 1963 1863 yards 133.07 pg
3) Walter Payton 1977 1852 yards 132.29 pg
4) Eric Dickerson 1984 2105 yards 131.56 pg
5) OJ Simpson 1975 1817 yards 129.79 pg
6) J Lewis 2003 2066 yards 129.12 pg
7) B Sanders 1997 2053 yards 128.31 pg
8) Jim Brown 1958 1527 yards 127.25 pg
9) T Davis 1998 2008 yards 125.50 pg
Hopefully, I didn't miss any big non-strike years in compiling these numbers. While I agree, folks are highly unlikely to just stop using the "yards per season" standard, this stat could be stated at the same time, showing a much more meaningful relation to the efforts of years past.
At the same time, think about the 1,000 yard season. It has been the "standard" of excellence for a running back season since the 12 game schedule. At that time, it meant an average of 83+ yards a game for the entire season. Now, it means an average of 62.5 a game for the season..not exactly something special.