Well, it may not necessarily be 5 campaigns for you, it depends on how many routes/flights you operate. But it'll be way more than just 1.

As Rushmore said, the system works only as a function of how much money you spend. The number of campaigns, the scales and scopes of marketing are nothing more than a little 'camouflage' over the fact that all you're really doing is choosing how much money you want to spend to increase your CI. Sami could just as soon just put a box there that let you type in how much you want to spend because that's really all you're doing anyways.

90-95 grows fairly slowly, 95-100 even slower, you may only get a 0.1 increase a week depending on how much you want to spend (the more you spend the higher you get and the faster you get there). You may have to spend 2 or 3 times what it took to get to 90 just to get the CI to go higher. It depends on your airline.