Currently, the Constitution places term length limits on Congressmen regardless of them being in the House or the Senate to a number of years. That system is and has been abused for decades with elected leaders just running for re-election time and time again.
In order to promote new blood and competition among our Congressional power in this country, it is vital to tack on term limits and more specifically, to limit Congress men and women to two terms each. By doing this, an individual may be able to buy their election with money and power, but after two terms, their time is.
The grandfather rule would have to state that anyone previously elected or currently elected has used up one term. They will only be eligible for one more term.