You must know frequency (or pulse width, as you call it) limits your circuit will be operational. Circuits don't work well under signal frequency outside of their intended range.
Typically you'd want to test your circuit for multiple transition (rise and fall) times. If I were to pick one, I pick 50%. For three I'd pick 5%, 50%, 100% and so on to cover the entire frequency range.
This topic is covered in details at paripath.com and in the book amzn.to/1N66Hds.