Yes, keep the spare. In addition to the sheer peace of mind it gives, it also allows you to fully rotate all the wheels around the car thereby get the best out of all 5. The instructions for the application of the dreaded goo require a certain amount of messing about in that the valve has to be in a certain place and you need to rotate the wheel to spread it about and so on and of course the final insult is that the tyre repair chappie won't repair it.
