Suet cakes in winter

Does anyone else find that the birds go off their store-bought suet cakes,when the weather starts to get colder? During the summer,I can go through 2 or 3 a day,but it tails off to the point where the cake has been there a couple of weeks and I'm wondering whether I should be throwing it out. I don't have this problem with my homemade lard ones btw.