In ancient days, a show came on at Nine p.m. on ABC on Monday night. The season began in September, usually the second or third week. It ran until May. Usually it was about twenty eight episodes in a season.
This allowed ‘breaks’ in transmission of the program for specials, be they sport, political, entertainment, whatever.
Imagining ‘then’ into the ‘now’, the first episode would air September Twelfth, then Nineteenth, on until May Twenty Ninth. For the months of June, July, August, and the first two weeks in September, that program would air ‘re runs’. The best fifteen episodes of the season would be shown in during the ‘summer break’.
Hence that slot, that Nine p.m. on ABC on Monday night, ‘belonged’ to that show.
In some cases, usually total errors, the show might be moved to another night, and often NOT take the fans with them.
However, the point of the re runs was to lock the fans in and not allow any break.
The allowing of breaks while some other show fills in often leads to the viewers finding something else, and by September ‘forgetting’ that previous series because they are not watching something on NBC.
These breaks are not good ideas unless they are filled with ‘alternative’ series. For example, if one watched NCIS and it took a break and during that break NCIS Los Angeles filled in, this would keep the interest in both series, so that Los Angeles could be moved to Wednesday at Nine.
When one watches on line, a break often leads to the watching of other programs online and in some cases, that first show is forgotten.
When watching on line one needs to select a very long series, for example, on that ran over seven seasons that had not been watched before, which is used as a fill in as one watches the new episodes of a program which is current.
If one moves slowly and carefully, one will begin season five when season seven is just beginning to air, and slow their viewing to the point that there is always a season in front.
In this way one doesn’t forget a program.