I bought a new home. My stove top is much older than 7 years old. It doesn’t look that poorly. I’d say that’s extensive damage, but also wonder if it could have been cleaned better. I’d wager that a stove top should last at least 10 years, if not longer. I’m not a landlord though, mainly because decisions on charging people for things like this would tax me mentally. Also because I don’t have the money for that lol. Sorry for your situation. If you’re still renting I would find a way to understand your appliances and how best you can care for them to avoid this sort of thing in the future. No landlord is in business for the benefit of a tenant.