I think that is a good schedule for you.. I saved this at one time from another post by a forum member and think it applies:
This is one of those questions that all depends on what you do with your computer, and how much you do it. If you just surf the net, write a few docs in Word, and maybe play the occasional game then defrag the HD once a month. If you do intense graphx design, play games every day, and download mp3's and movies then you should defrag your HD atleast once a week.This is also an interesting discussion
I fall into the category of "once a week", but sometimes I find myself not needing to. WinXP/WinOS's will anaylyze your HD/partitions and tell you whether or not you need to defragment them or not. Usually it's a good judge on when u should. When you defrag ur HD it basically moves all those scattered files and programs across ur HD's platter into neat blocks of data depending on how often you use them.
Now, Defragmenter is a HD-intensive app so yes it's going to put it through more stress than ur average use, but even if you defrag once a week your HD will last long after ur next upgrade (hoping that's within the next few years).
[span style=\'color:blue\']Defragmenting VS HD stress/life!?