Many have, but others didn't. For example, Mama's Family was a show that stayed true to its theme throughout its entire run. What other shows can you think of? They can be cartoons, too!

Friends and Seinfeld did a pretty good job.

Hannah Montana

Wow. You love Mama's Family? Love that show.

Yes, I do! I'm a huge fan and loved it growing up!

Friends
Full House
Hey Arnold
That's So Raven
Wizards of Waverly Place
Hannah Montana
The Golden Girls

Seinfeld

Friends

Lost

Desperate Housewives, In my opinion.

But it's very debatable.

Chuck!!! I'm so sad it ended

Chuck
Friends
Fringe(I think it's ending or over)
Bernie Mac show
Seinfeld.

Friends
Seinfeld
The Simpsons
The Cosby Show
Saturday Night Live
Oprah Winfrey Show
Grey's Anatomy
CSI

The Nanny.
Every character stayed for ever season EVEN when pregnant.
They wanted to change her to an Italian new Yorker instead of a Jewish new Yorker because they thought it didn't have mass appeal. She stayed the same and it worked. Favorite TV show ever.

Sister, Sister!

Nip / Tuck.

That;s So Raven

I LOVE LUCY

I'd say Doctor Who, but I'd be a filthy liar

A lot of the old 90s shows like Friends, Charmed and Seinfeld didn't. All of the Disney shows didn't dare. It's hard not to jump the shark nowadays which is a bit depressing. The only ones that havenm't done it yet IMO are OUAT and Vampire Diaries, but I have a feeling they're about to.

Gurl Lost jumped the shark more times than Doctor Who has in its seven seasons don't.

YES!