Let's get real here.

SS missions aren't even rare, you have a 3hr time frame with 2 free refreshes. That's assuming you do not have time to play in the afternoon or evening.

During this this 3hr period, i reckon you can get at least 3-4 SS missions on average.

If u just spammed the 2 free refreshes, i'm pretty sure you would get 1 SS mission.

I think you just want free refreshes so that you can pick the convoy with the highest coins no?

And it is a joke that you are bringing in free refreshes for plunder which is real time so obviously it should be spammable. Or better yet, change the interface for plunderer so that SS mission will just appear and you can click plunder, no need for refresh. ;P