Pages dealing with duration in Premiere Pro.
“Make a smooth transition in Adobe Premiere Pro If you have never visited the Adobe Design Center...Tutorial:Make a smooth transition
“Altered rates: Varying playback speed If you have never visited the Adobe Design Center site...Tutorial:Altered rates Varying playback speed
“There are tutorials in the Premiere Pro 1.0 and 1.5 online Help. From within Premiere Pro press...Tutorial:Premiere Pro 1.x Help