That's a good one, too, and I'll keep that handy.
I actually just figured it out on my own. If anybody wants to change the popup notification behavior, here's the steps:
1. Hit Start, type gpedit.msc into the search field, hit enter.
2. Navigate to Computer Configuration > Administrative Templates > Windows Components > Windows Update
3. The key in question is "Re-prompt for restart with scheduled installations". Double-click it to bring up the key properties.
4. Click the "Enabled" radio, and change the wait period from ten minutes to a value of your choosing. (I set the max - 1,440 minutes.)