> I imagine that while vegetables sources would be pretty reliable (fruit
always grows in the
> same place for a start)

That's never been my understanding. Considering that ripe fruit in the
primitive world would be quite a calorie-rich prize not just for humans, but
also for birds and other animals, I would think that gorging would be the
order of the day. IOW, if you don't eat all the berries you find today,
birds may have consumed the rest of them by tomorrow. Or rot may beginning
to set in. So it would make sense that, if you were lucky enough to find
fruit that hadn't already been consumed by other animals, to eat as much of
it as you possibly could.