Some good advice on here already, I'd back up that specificity is key. I've done a multistage organised event in a few years and that was VO2's Atlantic coast challenge (Cornwall) which was roughly a marathon each day getting more undulating and challenging underfoot as days went on. Back-to-back long days helped train for that.
But then last year did a self-organised multi-dayer last year, which saw me running on 5 consecutive days, but the biggest days were middle three at 53, 44 and 43 miles. Hauled all own gear, but travelled quite light as staying indoor accommodation each night.
Very different terrain to what you'll probably encounter as mostly undulating light trail and more tarmac as days went on. I'd trained with 30-65m weeks most of the 6 months in advance and had run a single 'longer' LSR most months of 26-50m, with an isolated challenge 85m run one month carrying lots of food and gear. All this mostly on trail. My peak training week was high mileage, 7 days run in a row with back-to-back 18 and 30m runs at higher than expected pace on the upcoming multidayer. Though, this was only time I'd consider I did back to back LSR. Other weeks typically saw an LSR on Sunday and 8m+ commute run with pack on tired legs Monday.
This prepared me excellently for energy levels, but could have done with more LSR on hard surfaces to try and reinforce my legs and feet against the battering they'd get on multidayer which turned out to have a higher percentage hard surface than I'd anticipated and usually done in training. Lesson here is I guess: know your terrain.
Looking at your specifics without knowing about the event, the daily mileage doesn't creep over marathon that often so you might not suffer too badly from impact damage, especially if more offroad. And hopefully plenty of time to rest each day after the run. As others say get used to running 5-7 days in a row and make the distance and difficulty variable. That 34k ascent is quite a lot so needs to be considered and factored in to you training as that works out at about 240 foot climb every mile which is not insignificant. If mostly off-road then this will mean quite a lot of walking, so practice LSR routes that are tough enough to make you do some hiking up hills and perhaps do a long hike at hard pace without running every few weeks.
Best of luck, quite jealous as sounds a good adventure.
Been doing some non-running prep in my lunch hours picking out the biggest climbs in Wolds from map for rep sessions or in hope of chaining together a route with most ascent/descent possible. Certainly no BourgStM length climbs!several in region of 500-650ft at my disposal and varying from (within 40mins drive) 1.1-1.6m. To put that in perspective a quick bit of maths suggests to me its about 5850ft from Bourg StM to Passeur Pralognan over about 8.1m - which includes some downhill as well - so this section still climbs more feet-per-mile than my local big (small) climbs
Not all bad news though, looking smaller there is a .4m hill with 349ft climb so repping that for a few hours would be a good if lunacy inducing session.
Hi Jon. No problem, hopefully others can post there thoughts too as some far more experienced heads on here than me and no doubt a variance of ideas on how to train to make this as painless as possible
If I've learned anything from my experiences in UTMB events to take forward to this one its got to be that the miles done on your long run aren't all important, its where/how you do them. This plan looks ok as a base in terms of your long distances, as I would if I could do most of my mileage at weekend in prep for this too. The old advice for ultra that measure your long outings in hours rather than miles makes lots of sense here.
You'd be best to add an extra level of detail into you plan to say what kind of terrain you'll do the miles on. Unlike a road marathon or even a runnable trail 50 or 100 miler the more miles the better in training won't necessarily increase chance of success here. Or at least only give mileage second billing.
I.e. If you run 80% upwards of the miles in your long run and end up averaging say 5-7mph, you are only training yourself to run long distances efficiently and fast. I'd suggest adding in a level of planning to set a target for the make-up of long runs. Its extremely hard to simulate the type of hills you'll ascend/descend on the TDS in the UK as even some of the smaller climbs there are the size of big climbs in Lake District, and hilly areas of Wales, Scotland...
The guys who live places with big hills and mountains probably don't have to think about this as much. But you, like me, might have the challenge of putting together some LSR with routes so hilly you have to walk significant bits. Within the limits of the smaller hills of Downs (I use the East Yorksire Wolds, which are similarly sized). I try to regularly do as many hours on my feet on routes which piece together as much continuous ascent-descent repeated as I can for this. Even if most of the climbs are 150-500ft or so, if done back to back you will likely have to walk many bits - especially if steep. This sort of LSR will be the backbone of my training I won't get much chance to escape to bigger hills. Long walking hill reps (ascent and descent) on the biggest steepest hills you discover - would be boring, but done occasionally could be tolerable and I guess would boost the hilliness to the max.
3x3000's sounds like a good event to use as training as works out about 260ft of climb per mile. I hope to get to Lakes to put some testing big climbs and time on feet into my legs, Bob Graham round recces, long fell races, 10peaks event courses etc would also be great prep as get you on some of the longer steeper climbs in England. As the key things to practice for TDS I would say are as below, as that's what a lot of the event is:
lots of walking up hills (the biggest climb is over 5000ft with the odd bit of descent thrown in, but not much). About the steepest is near the end.
running down, walking where needed, long and sometimes steep hills (again some of the descents are thousands of feet - probably as big a leg killer as the ascents).
still being able to run between the aforementioned