Professional opera singers, does your vibrato inevitably get slower as you age?

I've just watched the BBC's new documentary Maria Callas: the Final Act (aired 29/12/24), which takes a revisionist approach to the question of why Callas's singing degenerated in later. In the documentary, Will Crutchfield explains that Callas's vibrato at the beginning of her career was as slow as that of a 60 year old opera singer; and since singers' vibratos only become slower with age, Callas's late-career vibrato degenerated into an unpalatably slow wobble.

It's certainly refreshing to see a departure from the traditional, male-centred account of Callas's musical decline, which posits that Callas was led astray by Onassis (because women are merely puppets to be controlled by men, of course).

But as a classically trained, professional cellist, I'm querying the notion that a singer's vibrato can only get slower with age. I accept that it can be difficult to break deeply rooted habits, but I'm fairly confident I can make my vibrato get faster overall if I want it to, and with a fair amount of practice.

I'd love to hear what any classically trained singers make of this theory. Many thanks in advance!