From Wikipedia:
As of July 20, 2006, Danielle Reyes and Will Kirby attained one hundred days in the Big Brother house between their respective original seasons along with the All Star season. Since then, "Chicken" George Boswell, Diane Henry, Janelle Pierzina, Marcellas Reynolds, Erika Landin, Howie Gordon, James Rhine and Mike Malin have attained the 100-day mark as well.
Fellow BB7 All Stars houseguests Alison Irwin & Jennifer "Nakomis" Dedmon barely missed the mark when Alison was evicted first in BB7 after just 11 days, and Jennifer 2nd after 18 days, bringing both their totals to 93 days. Should either of them have survived their respective evictions, they would have both obtained 100 days.
Will Kirby holds the most days playing the game with 147, followed by Janelle Pierzina with 143, Danielle Reyes with 142, Erika Landin with 140 and George Boswell with 138 days.