Oil buzzer stays on until engine is warm?

I have a mk2 8v gti engine on twin carbs, and when you start the car theres no oil light or anything, but if you start driving the oil light and buzzer come on and dont stop until the engine is at its maximum running temperature. But if you sit there and keep it idling for a good 5/10 minutes until its got about as warm as it will get then the oil light and buzzer dont come on at all. I cant really remember but the last set of clocks I had (before the carbs went on) didnt have a buzzer, but I dont recall the oil light being on for so long, if at all. Is it possible that the clocks are at fault, or is this normal, or is there something potentially wrong?