Blastoff Labs does not believe in lock-in terms within contracts for PPC agency services. Those kind of terms are one-sided; our clients are free to discontinue use of our services at any time.
We have developed a superior way to lock in our clients that works far better, than “doing business by force of contractual language”. Of course, we do use contracts, mostly to set expectations and define terms of service. As far as client retention, we believe the only way to retain long-term clients is for us to do such a great job helping them meet their business objectives, that our clients worry we may decide to go do something else!
In our experience, the only retention model that works in any services industry is to constantly add value.