It's more an age thing with our cars really, mine has 36,000 on it and I last changed it 6 years ago, I keep an eye on it when I service the car and it still looks and feels fairly flexible.
You'll see hairline cracks on it and they start to squeal sometimes when they are older.
I would change yours if you think it's original, I'll change mine at ten years (on a time basis) if it still looks ok and not squawking away they are only about £15 here so cheap really compared to the alternative.
