When I first met my wife I used to become infuriated at her apparent inability to arrive anywhere on time. We had several memorable arguments about it - her wondering what I was getting so up tight about, and me wondering if I could ever have a future with someone who had such a cavalier attitude about time.
Over the years we've both made compromises - I keep my temper when she says 'I'll be ready in a minute' when I know she means 'I'll be ready sometime in the next hour', and she tries hard to be punctual when other people are involved.
My father, who was a military man, taught me that it's the height of rudeness to assume that the other person won't mind waiting when you're late. As a result I'm the one who would arrive before everyone else if he could, and I would rather wait an hour or two in the airport than arrive breathless at the boarding gate when the ground crew are about to close.
You are how you are, and if your friends are as late as you say, you are entitled to feel a little irritated.
I think that I would ring them. We made a dreadful mistake one day when we thought that our friends were coming to us and in fact it was the other way round. It wasn't until the telephone call did we realise the error.