No matter the brand or price, I would expect any bag to leak a little down. But at what point do you get concerned?
I have a Marmot Never Winter (30°) and it's really pumping out the feathers still after a year. I probably used it a few nights on the ground and 20 or so times in the hammock. Never washed, properly stored in the large storage sack. I may give them a call to see what they say.