Just not sure about the fee for a period of time
Me too.
Why? So you pay 0.05DRK when you want to mix, then you mix how ever much you want. If your client goes over 24 hours, it'll spend another 0.05DRK to keep going. It eliminates the timing attacks and double spending attacks.
people could still spam during that window and bloat the network for free, no?
DOS attacks? We could have a masternode sign the transaction when publishing it. The distribution should be really even among the masternodes, so that would eliminate bloat. So if you own 1 masternode, you could publish 1 transaction every 2 days currently. So it requires 1000DRK to use this feature and you still can't use it very much.