Fifteen year old adverts are about as permanent as you get: http://www.milliondollarhomepage.com/
A look at the page shows that long term ads are not as useful as they first seem.
Other than that, a short .com domain name can be used to permanently advertise whatever you want if you can afford to buy one.
Other than that, find a popular website and make them a deal. You advert will last as long as your credit card and the website. In reality that's isn't forever.