I created a ARIMA model with 1224 month wise data (102 years - From Jan 1900 to Dec 2002), totalling to 1224 data items. How far I can forecast. Typically i got some pattern in forecast only for 36 months ahead (Jan 2003 to Dec 2005) After that my values became constant only a straight line was observed. Can any one help me out with this ?
And any suggestions to build synthetic data with existing data in hand is also appreciated.