These days the NH campaign seems to be focused almost entirely around the Cheltenham and Aintree Festivals to the exclusion of almost everything else.
True to an extent, but I do think the NH season has a good structure to it from November to May:
Early season highlights in Nov / early Dec like the Hennessey, Tingle Creek, Old Roan Chase, Betfair Chase, Fighting Fifth and of course the Open and International Meetings at Cheltenham --> plus lots of novices making their debut
The superb Xmas / New Year meetings at Kempton and Leopardstown, plus the Welsh National meeting
January / February has lots of the big prep races for the festival (Adonis, Dovecote, Game Spirit, Denman Chase, Irish Champion Hurdle, Festival Trials day at Cheltenham)
And then bang - bang - bang you have Cheltenham, Aintree, The Whitbread Gold Cup and the Punchestown festival
Nicely balanced with high class races throughout. The spring festivals being the highlight of course.