No amount of time. Grizzling yes but crying no. Crying is their way of communicating that they need you.

If your really worried ask your GP. But I let it go for a long time at first because this process tires them out, after time this does not happen and they just go to sleep. Don’t fret, they are fine, as long as there in a safe environment let them try to settle for as long as possible. It hard I know, real hard as a mum.