Is adding new data to a model a full retraining from scratch? Or can it be added on top of an existing model? If it costs $10B to add 1 year of data to an exis

Is adding new data to a model a full retraining from scratch? Or can it be added on top of an existing model? If it costs $10B to add 1 year of data to an existing model, every year, that doesn’t sound too good.