Everybody has a different skin type and reacts differently to certain substances. Therefore, just because an Anti Aging Cream works for one person doesn't automatically mean it will work for you. If you're thinking of spending a large amount on a product then always make sure it comes with a guarantee. This is the best form of protection you can have if you find out that a cream isn't as effective as you thought it would be. You want a minimum of 30 days but one of 60 or 90 is much better.