Disabling the startup memory test may help reduce long boot times if you have a higher memory configuration.
Note: This option is normally hidden until you press and hold the Command and Option keys while opening the Memory control panel. The startup memory tests are designed to ensure that the memory is fully functional in the computer. You should disable the startup memory tests only if you are experiencing a long delay in starting up your computer.
Additionally, ensure that you have highlighted a startup disk in the Startup Disk control panel. Not having a disk highlighted can extend the startup time.
For additional information on reducing startup time, see article 31175: "Macintosh: Reducing Startup Time"