You shouldn't be getting anything popping up in the BIOS log so I can't see periodic clearing making any difference. I have a DG45ID with this option and in the 13 months I've used this model of motherboard, I've only ever encountered one entry in this log and it was generated around the time of a BIOS upgrade. Are you getting lots of entries in the log and if so, what for?
i was wondering if it was of any helpful benefit. like any other maintenance performed.
It won't do any harm but it won't do any good either (with the possible exception that if the BIOS log has any entries, a tiny amount of memory won't be allocated to storing the log). The main thing is that you shouldn't be getting any errors turning up in there so if you are (at all), resolving the cause (s) of those will be far more benificial than clearing the log.
I find the event log useful because it tells me what happen after a system event occurs. And the entry in the bios doesnt affect any normal system operation whatsoever. Now the question as to periodically clear the log, I would say that it should not. Just leave it as is as it does not bother the system operation.