op here: well, maybe it is time for a new one... it gets stored in an air-tight plastic bag thingy, so it doesn't smell at all, but maybe down has a life-span...

dryer balls also work

After 7 years, I'd replace it.

But yes, the tennis ball thing is supposed to help. It may have gotten damp in storage. Does it stink?

put it in the dryer with some tennis balls. I hear that helps refluff the down.

The head end probably compacts faster than the feet because of oils, heat, general use.

When I change the sheets, I hang the comforter over the banister for a few hours. Seems to help. Doing an end-for end swap should help it wear more evenly, too.

You could see if tossing it in the dryer with a few (clean) tennis balls helps to fluff it up more evenly.

Down can be washed if you have a large enough washer and dryer. Or you can send it out. You don't want to do it often, because I think it loses a bit of fluffiness every time, making it less warm, but occasional washing might be needed.

op here: i don't think its shakeable - the down is sewn into squares in the duvet, so all the down isn't floating around loosely in there - its actually in separate compartments and that's why i can't figure out how one end is so super fluffy and the other is flat as a sheet,

LOL, just shake it even. I shake mine out every week at least, if not every day, when I air out the beds anyway.

Yep they do that. When you go to replace it get one that is box filled. A good cleaning (expensive but worth it) will also help redistribute the down

the down in our comforter migrates. shake it out. i find it helps to do so from an elevation, so i stand on the bed, hold the fat, fluffy end, and shake until it's evened out.

so we've had a really nice down comforter for 6 or 7 years and this year, when i pulled it out from storage, it seemed slightly flatter on one end. i popped it in the duvet cover and put it on the bed and now that end, which i put towards the head of the bed, is totally flat and the bottom is a foot high (like a big down pillow). i switched its orientation - maybe the down is migrating to the foot of the bed, but i can't figure out how or why it would do that? but is there something i should do? can i wash down? will it even it out?