Hi,

Assuming you run log in normal mode, as me do.
I made very same experiences as you did.

Now I ended with the logsize of 400 mB and no problems at all.
Most of the time I have 
the maximal LOG utilisation of 2-3%,
but, as you said, every 3-4 months
it raises to 80-90%.
Yes, I still have possibility to EXTEND LOG
by 20 MB, just to be on the secure way.

The definitely sufficient LOG size for you 
will depend on your OPT file parameters,
sizes of the files you backup,
and composition of processes and sessions
you run concurently.

Bye

Juraj Salak,
Linz, Austria