This is a conversation between my boss and me yesterday:
"We got to submit this to our VP by the end of tomorrow. Follow up with John. (We need a set of numbers from John), he is not good at getting back to you when you request something".
"Right. I called him earlier and he complained that he is busy with other assignments."
"Well tell him we need it for Mike(our VP) and we appreciate his help. If he still doesn't respond by tomorrow morning, we have to "tramp" him. I'll speak to his boss."
I think it's OK to push your colleagues. But we have to do it professionally. Following up more than twice a day is a waste of my own time.
Besides, if I can meet my deadline, I won't push too hard. We, just like our Canadian colleagues, have limited "credibility capital", so we have to "pick our fight".
If you think you can make your boss "wow", go for it.
Have a good weekend