Change Refuse War Periods
12 Hours is fine. That is enough time to shake off any incoming attacks and get some sleep.
The next jump to 5 days is a little much. There should be a middle option of like 2-3 days. This would allow for people going away for the weekend to somewhere without internet to be able to put on RW before they left and continue playing when they get back. Otherwise they end up having to wait until the middle of the week to continue playing or risk their armies and cities while they are away.
I've also read several posts about a holiday mode which would be cool, but maybe a longer term RW instead? Say 2 weeks?
My suggestions
12 Hours - 20 Coins
2 Days - 40 Coins
5 Days - 50 Coins
2 Weeks - 100 Coins