
Unbeknown to many people, and despite being packaged in one convenient box, Honey Bunches of Oats is actually two cereals. Usually, the first half of the cereal consists of the various kinds of flakes with a few bunches of oats. After all that goodness is eaten up, you'll find yourself pouring a bowl of honey bunches of oats (like literally the honey bunches part) and a bunch of crumb-flakes.
I remember once reading on the cover that the contents of the box may have sifted, or something to that extent. Since then, whenever I buy HBoO I'll usually let it sit upside down for at least a couple of weeks until it's ready for consumption.
For the record, the flake parts of HBoO take a turn for the nasty around two minutes after milk is added but the bunches hold up just fine.
For this reason, when the cereal is remixed (usually by storing the box upside down and shaking the bag) and allowed to re-fuse to its intended state, HBoO reaches its maximum flavor potential.

Funny side story - we left the milk too close to the top of the fridge for a while and part of it ended up freezing. As an amazing side effect, the super cold milk seemed to slow down the sogification of the HBoO flakes and transformed it into an entirely different cereal, all for the better. It seems like it'd be kind of a hassle to keep the milk at freezing temperatures just to have perfect HBoO though, so I wouldn't recommend it unless you're pretty bored.