Never replace a fuse with a larger one. Ever. In this case you should not need to.

This sounds like a case of an intermittent open circuit. Or a loose connection to the layman. Somewhere.
I had the same issue recently with my foglight HID's. It, in the end, turned out to be a broken wire in the base of the bulb. The bulb/glass envelope was fine-the wire came off the contact inside the base of the bulb.
It would work basically when it was cold. Would not re-light.

Good luck.