Store hundreds of tasks per day per user in custom log sub-system

[eluser]CARP[/eluser]
Hi

I've been instructed to develop a custom log system for the CI app I'm finishing.

This log system consists of:
- 1 table with 5 fields. id:INT(20) | task_datetime | taskdesc | fk_user | value | comment
- 1 library with the "logtask()" function which writes to the table using the model_log model
- I autoload the library
- I do a 1 line call to the library's do_log() function in each controller's function, all controllers

So, my app has 12 controllers, 5 functions each avg. (most CRUD) and 6 users

Which would be the best approach so I can store hundreds of tasks everyday, during a month? I'd to a manual cleanup of this table each month

I've thought also about combining the actual MySQL database models with a plain text filesystem -only for doing this logging- (SQLite?). Could this be done in CodeIgniter?

Thanks in advance,