Orcs Must Die! 2

Orcs Must Die! 2

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Weekly challenge skulls
Hi, got a doubt. What does the weekly challenge skull say when it becomes available weeks after? Do the skulls reset?
Not talking about those you can spend, I understand you'll still be able to use what you got. My question is, my weekly challenge says I got five skulls. In, let's say, 12 weeks, when the challenge comes back, will it still say 5 skulls? Or 0 as if I've never done it?
Thanks in advance.