To begin with you can easily find videos on YouTube of people opening a 1000 of containers at a time (TYL ones) - approximately 1 in 20 would be a SC. I had approximately the same % of SC and I only do TYL ones for a very long period of time.
And to all people that actually think the most desired outcome is a premium ship.. seriously? it is one of the most undesired outcomes.. flags/camos etc are so much more valuable.
There is not a single prem ship that comes even close to free exp/coal ones for farming purposes.