I run long campaigns with fairly epic plots. I expect it to last at least a year. If someone has to bow out sometime during the campaign we’ll play around it and recruit a new player to fill the gap if needed. 7th Sea is a swashbuckling system with an emphasis on the dramatic over the realistic. Think of it as in the style of Pirates of the Caribbean or The Musketeer.
I don’t come up with a campaign plot ahead of time for this setting. Once everyone has submitted heroes I will think over their backgrounds and come up with a way to start the campaign. The overall plot will evolve from the character backgrounds and how the game goes.