Wow. I was born after this show went off tv. I didnt know it was on for 15 yrs ! Plus the specials ! That is great for a tv cartoon! Only the Simpsons has beaten it right ?( Interestingly just like how Simpsons beat Cosby show.
Well, because it was well loved, it stayed on for a long time. It did change a bit though. At first, you had the kids sing some song related to the episode, but later it was changed to them watching Brown Hornet and the lesson he learned the kids would use later in their lives.
It didn't air new episodes every year for those 13 years, though. It aired from 72-76 as Fat Albert & the Cosby Kids, then new episodes came back in 1979 as The New Fat Albert Show from '79 to '81 (this was when The Brown Hornet was introduced), then was off for a few years until it came back as a first run syndicated series titled The Adventures of Fat Albert and the Cosby Kids from '84-'85.
Also the seasons when it did have new episodes, they were usually short seasons. Season 1 in 1972 had 14 episodes, then most of the other seasons had 6 or 8 episodes a season and they just repeated them the rest of the year. By the time 6-8 weeks went by and they showed a rerun a small kid probably wouldn't remember that they had seen this episode. They did this a lot with the '70s Saturday morning cartoons. They did small seasons, then just repeated them over and over.
I used to watch this show every Saturday when I was a kid from the time it premiered. I was 5 in 1972. I also watch a lot of the other cartoons of the time and didn't realize until just a few years ago that they didn't make very many episodes of most of those old cartoons. Most were just 16-22 episodes total and aired in repeats for years.
Fat Albert did get 110 episodes across all it's different incarnations, but like you said it was spread across many years. Almost half of those 110 episodes were from the '84-'85 syndicated version of the show which had 50 episodes that ran straight through with a new episode every week. There were only 60 episodes spread across the 4 seasons of Fat Albert & the Cosby Kids (1972-1976)& the 3 seasons of The New Fat Albert Show ('79-'81).