You wouldn't want to do business with an insurance company which only sold a particular type of term policy or whole life policy, proprietary to their own interests. Nor would you want to do business with an insurance company that told you that you had to keep paying them for some specified number of months or years before you were free to shop for a different insurance product elsewhere.
Why, then, would you ever consider binding yourself into a term-contract with a marketing company that only offered one category of service, or that requires you to pay them (regardless of your satisfaction) for a lengthy period of time? It just doesn't make sense to do business that way. Another rule of thumb: Your search engine marketing efforts should liquidate their own costs in reasonable time by producing results from the campaigns that you run.
Otherwise, your advertising efforts are a money-losing liability, meaning "a bad business decision." Tobe effective, your campaigns need to be managed and adjusted each month, not just treated as cookbook recipes followed blindly. To verify that you are getting the results you deserve, you should have access to some combination of reports, updates, and analytical metrics (data) displaying your progress from one month to the next.