A timeline I saw had the South Tower staying up for almost exactly 1 hour after it was hit, and the North Tower up for about 1 hour and 45 minutes after it was hit, or about an hour and a half after the second plane hit the South Tower.
I've seen other accounts that disagreed with these times.
You're correct; I just rechecked the Time Magazine chart about this. Tower 1, hit at 8:45, collapsed at 10:29. Tower 2, hit at 9:06, down at 10:00.
If you'd asked me that afternoon, I would have sworn on a stack of Bibles that both towers were down in way less than an hour (but then, I did have that memory glitch I mentioned).