argh.

i took my fabia to get diagnosed at my local rip-off dealer. they replaced the temp sensor, stripped and cleaned the throttle body and replaced the brake light switch.

so that came to

It depends on what was causing the light.

And there are many things that cause it.

Broadly speaking, if an intermittant fault is detected - and then does not reappear, eventually after so many engine starts, the warning light will "switch off". I suspect that is what you have seen. Obviously "hard" faults will keep the light on until whatever was causing the fault has been fixed - and the fixer will normally clear the stored faults.