Up until about 1972, a JW could not even be deemed a "Regular Publisher" unless they met the minimum quota of 10 hours per month. Added to that, they had to have also conducted at least one bible study, placed at least 12 magazines, and made a certain number of "back calls" during that month - or else! (Particularly if one failed to "place" those 123 magazines, in which case that same said person was liable for the JW equivalent of "No.1 Field Punishment").
For those interested, WC Stevenson's 1967 work The inside story of Jehovahs Witnesses gives a full description of the complete matter of "hours", as it then stood. Certainly, when I first began attending meetings at the Kingdom Hall (circa 1970), that is all you seemed to hear about.