...would produce a fifty-year hit to the primary deficit of $4,000,000,000,000--although the number is ambiguous because the interactions with other tax provisions, especially the AMT, is so large.

Just as it was a catastrophic mistake to pass the Bush tax cuts in 2001 and 2003 without triggers to reverse them if the structural deficit became a problem, so it would be a catastrophic mistake to permanently extend any portion of the Bush tax cuts without triggers to reverse the extensions if the structural deficit remains a problem.