Building from source takes time because it takes a significant amount of processor power to turn source code into binary executables. It doesn't matter what platform you use (Linux, Windows, MacIntosh, etc.).
An 8MB source package can take a very long time to build.
Binary packages, in contrast, really only need to be copied to the hard drive.
The distinct advantages of compiling from source
are: the ability to customize the compile to your hardware, the binary will be linked directly against libraries on your hard drive (insuring maximum stability and compatibility), and you can specify compile time options.
To shutdown your linux box do one of the following
1) as root type /sbin/halt
2) as root type /sbin/shutdown -h now
3) hit CTRL-ALT-F1 to go to a text console, and then hit CTRL-ALT-Delete.