>>717050245
It was pretty gradual, and he kept compensating by going higher, until about 2016. Then he went off a cliff. That's also when he stopped taking roles in absolutely everything and got a lot more selective. A lot of the voices he's known for are obviously pretty hard on him. He has to strain to get them to sound right, and now the consequences of that are just too significant to ignore. That's the difference between voice actors who nail a single performance for their whole career, and those who aren't able to stick with it.
Kevin Conroy's Batman and Peter Cullen's Optimus Prime are examples of the former. Those performances weren't as fantastical, and as a result, they don't wear their voices out, even over a long time.
Not that it's impossible to do voices like that for a long time and stay the same, Frank Welker and Steve Blum are proof of that. But out of all the roles Tom Kenny has ever taken, maybe a handful of them were "easy."
Just compare him to Bill Fagerbakke, Doug Lawrence and Rodger Bumpass.
Bill Fagerbakke's "decline" is mostly due to direction and the flanderization of Patrick as a character. There was a recent episode of the Patrick show where he happened to deliver a line that sounded exactly like he did in Tea at the Treedome.
Rodger Bumpass has always given more or less the same performance regardless of role, he sounds the same as the Chief from Carmen Sandiego as he does as the mosquito from A Bug's Life, and as Squidward.
And Doug Lawrence also usually sounds the same, but the only taxing parts of his roles are usually when his characters are screaming, which isn't nearly as bad of a duty cycle as Tom Kenny gets.
>>717051078
Stephen Hillenburg was thoroughly involved with the episode Feral Friends, which was a nod to the IP's original premise as an educational brand for marine conservation.
