As mentioned, it all depends on your goals. Even though I'm spending most of this year working on 5k/10k PRs, I'm still pushing to keep myself at half readiness. When you get to the point where you can crank out a half without much thought, it just becomes another training run with maybe a slight speed/mileage drop for a few days. But if your goal was a half, and you plan on dropping back down to 5k/10k, then most people would suggest a week of rest/cross training, with a bit of drop back or taper on your mileage the following week. But even more than that, depends on what you did at/during the race. Being able to simply complete a race is completely different than cranking something out at a PR pace. If you had been training for a 2:00 half, but then got sick, had cramps, whatever and ran a 2:15, you could do more during that following week than if you had kicked your own butt, and ended up pulling out a 1:58 PR. If you do nothing and take the entire week off, it's not a pretty sight. You definitely need to continue to do something, low impact is fine so bike cross training is great. After Dopey instead of 2 runs/1 bike day I did 3 bike days, and then did lower mileage on my long weekend runs.