I'm new to TS modeling, but have some experience in classic classification modeling. In classification I can train one model and use it for some time while some indices are stable (e.g. PSI).
Assuming I want to forecast daily demand on bread. One day (31 DEC 2013) I've trained ARIMA model and made a forecast for tomorrow (1 JAN 2014). Is there any way to use this model tomorrow (1 JAN 2014) without retrain it on new data (demand before 1 JAN 2014 and demand on 1 JAN 2014)?
The reason to ask: in case of huge amount of goods it requires a lot of time to retrain all models everyday. Retrain it once a month (like in classification usage pattern) will be better.