I know this has been discussed previously, and sorry for bringing it up again, but I am hoping to get some specific advice. I have an upcoming 100k with a lot of climbing, and I expect I'll need most of the 116hr cutoff to finish the race. I am now planning out my long runs and routes, but I am not sure what my max time in a run should be? I've heard that after a certain amount of time and/or distance the cost of training is too great as it requires a long time to recover essentially negating a lot of the physical benefits from the training run. What are your opinions and experiences on this? An example of some of the training runs I can do is a 20k 4:30 loop through the mountains--the slowest I could do 20k I think, but over 1000m of climbing and lots of downhill. Should doubling this be enough even though it is only 40k? Thanks.