I save before and after bosses in games and when I see a save point. In Pokemon I used to save a lot, like every time I leveled or healed at the P.C., but I've heard its not good for the internal battery when you save and load too much, so I don't save so much anymore. But since my Pearl just froze for some unknown reason, I save a little more often at DP in case it happens again.
My Gold and Silver batteries lasted longer than I've heard most people's did, and I got them before release (Woo! <_<), and I save tons, as I've stated.
So, maybe an odd case, or that's just speculation. I dunno.