I have trained a model for predicting the sale of items daily, such as daily car sales, with a machine learning model in Python. Now I get the new time real data (time series data). I want to retrain my mode. There are some issues:
How much data I should use for retraining model, namely what's the time range of data or when I should retrain my model. For example use the new one day or one week et al., data to retrain model.
What's condition of new data if I want to use the new data for retraining model.
How to evaluate the stability of new training model, and How to know abnormal prediction for new model.