How long do gravel tires last? How many should you bring to an event?
In general, you can buy gravel rally tires in soft, medium, and hard.
Softs will last you a couple stages. The whole plan with softs is to change them at every service.
Hards will last for years. They just get rounded out, beat up, lose their grip, the tread blocks lose their sharpness, and they get handed down from one team to the next, collecting dust and stories.
Mediums will go a rally or two on 'regular' cars.
For new guys starting out, you'll need seven tires: four on the car, one in the trunk, and two more as spares. That will be enough to get you through your first rally.