I know that this isn't a cure, but it might help if it works on your car like it works on mine.
I have same issue with my car sometimes. All bulbs are working and none have been replaced recently.
I find that the bulb warning light stays on for the whole journey if it's on at the start.
However...
If, when I start the car the warning light comes on, now what I do is turn on the headlights. The bulb warning light then always turns off after about 1 minute.
Having done this, the warning light never re-appears during the journey.
Hope this works on your car too.