When Should a Machine Learning Model Be Retrained?

A few years ago, it was extremely uncommon to retrain a machine learning model with new observations systematically. This was mostly because the model retraining tasks were laborious and cumbersome, but machine learning has come a long way in a short time. Things have changed with the adoption of more sophisticated MLOps solutions. Now, the common practice of retaining a machine learning model is somewhat reversed. Models are being trained more often and after very short intervals.