WOW! Looks like we've got some power users here!
Anyway, your feedback definitely gives readers some idea on how much batteries are required. However, we should use the number of images taken for each full charge (including flash shots) as a benchmark. Therefore, it all depends on the event that you cover.
If you intend to take 1000 shots in a day - all flash, you bet not even 3 batteries are enough (I think for other digicams, you may need 10 batts!) . However, as an average user, I think one battery should be able to last one day before you recharge the battery overnight. Of course conditions vary, but F828 is definitely better than 90% of the consumer digicams out there, some barely can last an hour of heavy usage!
It's the same as asking: how much CF cards do I need for a vacation? Again it all depends on how many photos you want to take.
Personally, my experience with F828 is that the battery indicator is accurate till the last minute. Therefore, you are able to plan your photoshoot based on the remaining battery life, and won't be surprised with battery-low situations and the fear of the digicam dying on you anytime.
So my advise is: don't buy extra batteries for the sake of buying. Buy only if necessary. Not forgetting the external charger to charge extra batteries, since F828 doesn't come with it.