A good spray can paint will last two or three years of regular outside exposure before deterioration becomes noticeable.
You can have any color of automotive paint put into spray cans. Although it is more expensive, that paint is much better than any standard off the shelf spray paint. There may be an automotive paint supplier in your area that does it, or there are places on the internet that do it. Tower paint is one of those, but not they offer different levels of paint quality.