I have a HM in September and run 10k once a week right now (with 2 X 5k) per week. Planning to steadily increase my weekly long run until I can do the 20k. I will keep my eye on my legs and continue to have running rest days. Does that seem a sensible plan? I run mostly on grass and trails so hope running up and down hills and uneven tracks is making me fit enough. Would I need to reduce my distances before the event and what sort of after event distances would be best?