Although curiously the actual data isn't that scary - 34k and 2900m up/down in Tunrbull's Lakeland challenges. Awfully rough terrain in a lot of places though.
Thats actually for the full route, but I doubt if thats much harder. Seatallan vs Yewbarrow is slightly further I guess but probably rather easier. And the screes aren't much extra distance or ascent.
Suppose the fullest route (from Ravenglas, including Muncaster) is the Irt watershed, which would certainly make a logical two/three day camping trip by train.