Depending how much you spent, determines how far out your break-even point is. Because higher upgrades are exponentially more expensive with only minor improvements, upgrades will require much longer to breakeven.
With the recent change (and future ones I predict will be coming soon) to rewards, it will take a lot longer for most people. A lot of people will never break-even, even if they don't spend a lot depending on when they sign up and how many people sign up after them.