It seem seem from 'The History of Morris Dancing'

http://www.wickham-morris.org.uk/main_history.html

'Going back further, it would seem that Morris Dancers used to dance each year, usually once at Whitsun. But having said that there seems to be a wealth of different oddities of tradition. For example in the Forest of Dean there was a procession headed by a man carrying a long pole with white flag and two front dancers carried swords used for very complicated movements'.

Obviously why they rehearsed for many weeks!