Hi Emmilou
I've changed my training this year and I feel loads better for it. It may be that another year has built up my strength/Stamina due to muscle memory but for what it's worth here is my view for Ultras.
Distance is not that important where as time is. Last year i used to train by going out and running as hard as I could for whatever distance and then spend 4-5 day recovering.
Now I run for longer over the same course but are able to get back out within 1-2 days.
i.e if I run 5 hours for 20 miles i get out and run again much sooner than if I went out and ran it in 3.5 hours. when running ultras it's all about keeping going for long periods so slow down but go longer.
Re walking uphill. Always on the long routes, it tells near the end.
Doing a 20 miler tommorrow so perhaps I should put the wine away now...
Ian