All I can tell you is what I do, you have to make your own decision. Lots of thing have changed including Apple's recommended routines. I used to repair permissions after every update, now I only do it after an upgrade — if I remember to do it then. I used to run volume repair regularly, but that was at least four of five years ago. I also used to defragment the HD every few months, but that was even longer ago. I don't even remember the last time I ran the daily, weekly, and monthly log recycling routines.
Now I have a utility that checks the system memory at least once a day, runs an I/O check and monitors the Power on Self-Test; checks volume structures at least once a day, performs a full surface scan when I am not using the system, monitors the S.M.A.R.T. readings, and checks the file structures daily. I have not had an alarm of any type from this system in months. The one I use is Micromat's Checkmate and it appears to me to be the most complete if for no other reason than the surface scan, but Micromat's TechTool Pro, Prosoft Engineering's Drive Genius, and other utilities offer some (most?) of this kind of routine monitoring and testing as well.
This saves me a lot of time, as well as providing advanced warning of impending problems. With this level of continual monitoring and testing I see no reason to perform any sort of routine maintenance.
