How many hours to pass in between doubles? 4 hrs? 6hrs? 8 hrs?

I've found that waiting about 5 to six hours provides enough recovery. Four is a bit too soon, and waiting for 7-9 hours allows the body to not be as ready, or primed. But life forces runners to adjust to doubles. And sometimes on doesn't have a choice as to hours between runs.

Need a minimum of 6 hours from when your run ends until you should do your second run. Gives the body enough time to recover and then it will benifit from the second run. Almost no point of running again if you do it before 6 hours, not saying that 5 hours between is pointless but less then 4 hour rest is pushing it.

I do doubles four days per week (usually). I get about 11 hours between and that works well for me. Before my work schedule changed, I was getting about 8 hours between and that seemed fine, too.

Different theories out there. I know I used to hear if you give it 8 hours between runs, it's two runs. Kenyans use the 6am, 10am pattern a lot. Not a bad idea because you can get 20 hours of recovery. Lastly, I remember a thread by Jack Daniels (whom I realize I haven't seen descend to this site in a while) saying that the idea of separating runs is somewhat arbitrary from the perspective of stress and recovery.