Forever ... or at least as long as the Bills are in Buffalo. The Bills franchise has been around for more than 50 years and have sucked the vast majority of that time.
They expect, and will get, significant support just as long as fans have hope at the start of the season like they did this year.
My kids even take it in stride now. They are still fans and wear their Bills stuff to school during the season. But yesterday for example, they were expecting a loss and were disappointed in the extreme with the performance. They were over it shortly after the clock mercifully ran out in the 4th.
It might be easier for them however than those of us that saw the early 90's. In their entire lives they have never seen a good Bills team.