I am reviewing whether I want to continue these monthly giveaways, as I seem to be spending more and more time chasing down winners...
First and foremost, you shouldn't let any of your activities or posts on this site become a chore.
You can add in your mail that not replying within x hours will cancel the prize.
If you see that most of those that don't reply are with a low number of posts, or from abroad, you can choose a higher post requirement, or make it USA members only.
In any case, thank you for the generous mystery packages that you took the time to send so far.