Breaking habits

I wonder if anybody else who has stepped up their training from regular "10-20m long run, speedwork, tempo, easy runs 4 day a week type plans" to something more suited to multiple stage runs and ultra's has found it hard work to let go and adapt to a new way of training?

As I've not done a short race this week and don't have many planned in rest of year I would probably hit the track tonight for some speedwork. I haven't been in a few weeks and have been mulling over pro's and con's of doing it. However I've come to the conclusion that with my next 10k a week on sunday there is no point and I'd be better off doing something more tailored like a mid pace hills run on this and future Wednesdays. Then do my usual offroad hard session (hills, reps, tempo) with club tomorrow, as this is a hard session and I think more useful than speedwork on track.

So I think i've made my mind up but any comments from experienced heads appreciated. My end game over next 3 months is the Atlantic Coast 3 day challenge (http://www.runnersworld.co.uk/events/viewevent.asp?sp=&v=1&EN=43290) - 3 days, 3 coastal marathon along the cornish coast finishing in Lands end. The distance isn't unfamiliar but multiple days running is. My basic plan is something like:

Monday - X-training or day off.
Tuesday - Undulating multi-terrain.
Wednesday - Hill repeats or hilly mid length run.
Thursday - Club hard sesh, usually off-road, often hilly/undulating, sometimes reps sometimes more tempo.
Friday - X-training or day off.
Saturday - Long run, 15-26m, maybe LDWA or FRA event.
Sunday - Shorter long run, 10-15m, maybe LDWA or FRA event.

It'll be a good kick up the arse for my training which isn't usually very structured at this time of year. Still working hard but with more emphasis on terrain and distance. Though I've done plenty of hard Saturday and Sunday runs I started in earnest yesterday. 4.6m on road, good trails in the Country park near Humber Bridge and on the stoney beach of the humber. Easy and short but as part of its in an old quarry there are some good short step climbs to blast up and down. Felt great running in the trees with the raindrops hammering the canopy above which wasn't quite stopping me getting soaked!