What if examiner stops you?
As far as my knowledge is concerned, I think examiner is not stopping you because you spoke awful English. It is only because you have produced enough language or the examiner is pretty much satisfied with your English language fluency.
Even the cue card instruction clearly states that you should speak for 1 – 2 minutes, that means more than one minute but not more than two minutes. So, the examiner can stop you at any time after one minute is over.
In fact, you should be content because the examiner is happy with your language and he/she doesn’t need to check your ability further. So, without wasting any time, she would directly move to the third part.
Personally, I feel that you should continue speaking for two minutes because that way you can produce much more language to impress the examiner.