Would doing 10k training adequately prepare a runner to do well at any distances between 5k and Half Marathon at any given moment? For example, say I base my running around 10k - type training and tomorrow I want to run a Half marathon, but two weeks from now I want to run a 5k. I don't want to focus on one specific event, and want to be able to mix up my races (of course sacrificing some time by doing so) and do well at various distances. I basically want to have fun running fast at different distances. Is this a good approach?