I keep a system of over 15 machines running 24/7 without the need of installing ANY kind of maintenance software.
That doesn't mean that I don't use maintenance software, that just means that I don't install maintenance software.
Even back in the day of Norton Utilities under OS 9, I found that installing the software was useless. Few utilities could make repairs to the drive while booted from the drive under OS 7/8/9, and under OS X, it's impossible... Don't install anything, and simply boot from the DiskWarrior CD when you need to check/repair the disk.
I still have no clue as to why these utilities insist on trying to get you to install the software on the boot drive. It's useless. Even with external drives, it's safer to boot from the CD to check the disks and make repairs.