Some of the best ever (Devaney, Bryant, Paterno, etc) has seasons near or below .500. Nobody WANTS .500 seasons, but to never expect it to happen is arrogant. It's not fair to expect another Tom Osborne.
We have 3 non-conference games ... we should expect to win 2.5+ of them each year. That leaves 9 conference games ... sometimes the schedule is stacked (like this coming year) but even then I would think given Illinois, Purdue, Indiana, Maryland, Rutgers, NW and Minnesota truthfully being Nebraska we should win the majority of those games year-in and year-out. Yeah we lost occasionally to Iowa State and Kansas in the old Big 8 days ... but I would expect against those 7 we should be winning 6 out of every 7 times. The remaining OSU, Michigan, MSU, UW, Iowa and PSU ... we should at a minimum break-even over time.
Yeah the conference schedule is unbalanced but using the West
... Iowa/Wisconsin = 1 win each year (if we're breaking even)
... The remaining (NW, Minnesota, Illinois and Purdue) = 3+ wins each year
So I have 2.5 wins from non-conference, 1 win from Iowa/UW and 3 wins from the other West team ... that is 6.5 wins each season without counting the cross-over games against the East ... so 7 or 8 wins minimum each year with a re-energized Nebraska program - with the correct coaching staff ... is not unreasonable.
Could SF have an occasional 6-6 season? Maybe, possibly, depends on the circumstances but I would argue that if he doing the job correctly then we really shouldn't have such a record ever. When's the last time Ohio State had a 0.500 season?
(FYI 2011 and before that it was 1999.) How about Wisconsin? (FYI 2001)