Well, that sounds like a complicated question.
In my case, take Tom & Jerry and Looney Tunes for example. When I was 4 to 10 years old, I grew up with Baby Looney Tunes, original Looney Tunes and Tom & Jerry (1940s, 1950s and 1980s version). Even though they are too old as of now, there are still Tom and Jerry memes (usually from the 1940s and 1950s version), which are more popular than the Looney Tunes memes.
Now lets talk about SpongeBob. Every big and loyal SBSP fan know that Seasons 1 to 3 are comedy gold. This is where we found the funny scenes to be used as memes (e.g. SpongeGar (SB-129 version), How tough are ya, world's smallest violin, etc.) Memes from S1 to S3 are way funnier than from S4 to present.
What's ironic is that SpongeBob not only become popular for kids but also became a cultural phenomenon in the 2010s. We all use memes and time cards from SBSP. We also relate the show to other issues and phenomena like demographics (e.g. millennials), world news (e.g. COVID-19), etc.
So, for the question? Just like the classic Tom and Jerry, the SpongeBob series would probably last a lifetime; and so as the fans. In terms of generation, most SB fans are zoomers (generation-Z) and millennials (generation-Y).