Barker hosted what, about 6,500 episodes*? A quick Google tells me episode 6,000 aired in March 2004; ep. 7,000 was November '09.
I'm guessing he did about 200 episodes a season, so even with the first ten years missing, they'd have about 4,500 episodes to work with, give or take a couple hundred. But I think they'd keep it to just 80s and early-90s era, which still gives them a couple thousand to use. Go from 1982 to about 1993, and cherry pick a dozen episodes from each year. They would repeat no more than the MST3K or Unsolved Mysteries channels that repeat every few days.
*Don't need an exact number, just spitballing here.