In reply to kathrync:
I can't see you having properly knackered the down in it. I think a professional cleaner that gets the down out of the bag, cleans it, then sticks it back in again would make it good as new. The problem with washing at home is it simply doesn't get into the down, especially if it's a thick bag: even with a huge washing machine, the outer fabrics protect the down so well, and they need a lot of washing and rinsing, that the down in the middle may never truly get washed. Incidentally, tumble drying will puff your sleeping bag up too, but again it's quite a temporary improvement.
Replacing the down in a bag is an option but - though I sure Mountaineering Designs know a lot more than me about this - I can't believe that you can ruin your down enough in normal use that it needs replacing unless you have spilt nasty chemicals on it or heated it to well over 100 °C! Down is so much more durable and long-lasting than many people think. Royalty have been using the same eider down duvets for hundreds of years and would replace the cambrics repeatedly before thinking about replacing the down.
Post edited at 17:07