I noticed recently that the headlights on my 2000 ST1100 were sometimes not working, other times were on.
As both globes were showing this problem, didn't think it was likely to be a globe replacement issue.
Was a bit concerned that I'd have to get into the innards to check the wiring, but thought I'd do a wider search on the forum to see if an answer could be suggested.
Found an older thread in this section which suggested that sometimes the starter switch doesn't return fully and cuts off the lights (when starting, the lights go off, should come on once the button is free).
A good spray with the fish oil spray, left for 20 minutes and hey presto, lights working again.
The value of the forum. Saving heartache and headache.