The Solaris 8 MU7 installation time varies depending on:
CPU speed of your machine
install_mu option you select
Transfer speed of the CD-ROM drive, hard drive, or network you use to access the install_mu code and patch set
If you install the MU7 with the backout option disabled, installation will proceed more quickly. However, you will not be able to back out any of the patches MU7 delivers.