Re your Mac sleeping at night:
Additionally, if your machine does not run 24/7 so that it runs the daily, weekly and monthly Cron Scripts in the middle of the night as intended by Apple, run Cocktail (shareware) as well.
Cron Scripts are maintenance routines designed by Apple to run on a daily, weekly and monthly basis in the middle of the night.
If you don’t run them, you WILL run into trouble, sooner rather than later.
Here’s an excerpt from the Apple tech doc <
http://docs.info.apple.com/article.html?artnum=107388>
Mac OS X performs background maintenance tasks at certain times if the computer is not in sleep mode. If your computer is shut down or in sleep at the designated times, the maintenance does not occur. In that case, you may want or need to run these manually.
Mac OS X periodically runs background tasks that, in part, remove system files that are no longer needed. This includes purging older information from log files or deleting certain temporary items. These tasks do not run if the computer is shut down or in sleep mode. If the tasks do not run, it is possible that certain log files (such as system.log) may become very large.
Also, from: <
http://docs.info.apple.com/article.html?artnum=106978>
The disk activity generated by find is a normal part of file system maintenance, used for tasks such as removing invisible temporary files that are used by the system. It is scheduled to occur early in the morning at 03:15 everyday, 04:30 on Saturdays, and 05:30 on the first day of each month.