Kepler was launched 4 years ago, so I think your first sentence is misworded. Its original 3.5-year mission was pushed out 3 years due to issues with noisy data

Kepler was launched 4 years ago, so I think your first sentence is misworded. Its original 3.5-year mission was pushed out 3 years due to issues with noisy data, so it hasn't really completed its original mission yet. (Not that it hasn't done a great deal of excellent work already, but much more is/was still to come.)