I´m no fundamentalist when it comes to bikes. I´ve got several bikes for different types of riding. But I see your dilemma; the roadie are designed for hard and long runs and thats what you need. But, will there never be a day when you want to ride a bit off road or mixed surfaces? Then you really dont want to be sitting on slicks. You can never have too many bikes (but I`m bias mind you!).