I still want to stress that even convoy takes time, you need to check every 30 minutes if you are unlucky and don't get good S mission or SS.

It happened often to me to arrive at the end of the day finding only one SS even with the free refresh, so it's not true that it takes 5-10 minutes to do convoy, unless you do whatever you find, even A missions.

I still think SS convoy should either be free or if you spend ingot, you should not be available for plunder, the coupons should be guaranteed since you are supporting the game with your daily ingot donation, while plunders are not supporting anyone else than themselves.