long rides and runs for half ironman training?

I've followed both the "beginner" HIM plan twice and the "silver" level 20-week HIM plan twice from this site. The beginner one was a little short, IMO, on biking time so I increased the long rides to equal 56 miles during that plan - rode the course twice before the race. On the silver plan, the heaviest weekend was:

Sat: 3h 30min bike, 4000 swim
Sun: 2h run

That plan has 2 more 3h 30min bikes after that weekend, but shorter runs the next day (80min and 90min).

I personally think doing your longest ride and longest run on back to back days will let you know what it feels like to run on tired legs - which is something you need to know for this distance. Other people believe splitting them up (at least 2 days inbetween, if not a week) to get a more quality run (not on tired legs) is more advantageous. Different schools of thought on that question.

I did long ride on Sat, long run on Sunday up to 116 bike, 17 mile run for IM training.  You pretty much need to get a long run and a long ride in every week, so alternating weeks for a long workout would really limmit your training.  You don't have to do them back to back, but you can.  I would say just get them in, in the same week, however that works for you.  You will recover from whatever (typical HIM) workout you do in 48 ish hours.   

same ballpark..

3.5-4 hour ride, 4000-4500 yard swim, and 2 hr run...  (my LONGEST workouts)

Longest ride: 59 or 60 miles. Did 2 of these (maybe 3- don't remember), one 50 miler and several 40 ish rides, some of those as bricks with a 4 mile or so run afterwards. Longest run was 12 miles but I did those too early in the plan and never did a long run in the 6 weeks before the race. My plan typically had the long ride on the weekend and long run on Wed/Thurs. If I do this again I might do three 60 mile rides and maybe one longer (like 80 miles) ride. Those long rides are harder to schedule with other obligations so take the most thought to get into your training. Check out some of the plans on here to get a sense of the kinds of volumes they suggest. Here's the one I used but others might suit you better:
http://www.beginnertriathlete.com/cms/article-detail.asp?articleid=52

My standard Sat ride was 55 miles.

My long rides (3 or 4 of them) were 75-80 miles.

My long run was 13.1 miles. I get injured easily and not a strong runner anyways.

I did not do any long bricks. I did some short bricks... with hill repeats (16 miles) and then running 3 miles.

After reading multiple books and one season experience, here is the long answer, you take it from there.
Depending on your current level of fitness, primarily endurance, considering your limiters, your goals (whether to only finish or to compete, using linear periodization: 
Swim: build to 4000-4500y, once a week
Bike: build to 3.5-4.5hrs, once a week
Run: build to 2hrs, once a week

Pattern is 3 weeks build, 1 week cut volume by 40%, reduce intensity, maintain frequency. That would mean that every 4th week no long swim, bike or run.
What has worked for me is: Monday long swim, Thursday long run, Saturday long ride. I think that it is important to keep long bike and long run apart as they will affect the quality of each other.
This is only one of the ways to do it. This only addresses the questions you asked. There is more to it and it is also about quality of these sessions and the overall program layout. You will get more quality advice here, consider it all and take for yourself what you think is appropriate. There is more than one correct answer here. 

This depends for athletes but IMO you'll be better prepared if you at least do the entire swim and bike distance and depending how fit or new to the sport you are either the whole run distance or at least 10-11 miles. How often is not as important as how much total training you do. That is, the sum of all your sessions is more important than 1 specific session. For instance, if you build to ride the entire distance (or close to it i.e. 50 miles, 3 hrs, etc.) if the more you do it the better. Of course for newer less trained athletes this might be a tough task hence doing it once or twice will be enough. OTOH if you are a more seasoned or fit athlete then doing it several times might be appropiate. My advice: pick a plan and if you need more, add a bit more slowly, if it is too much adjust accordingly, just be consistent.



I posted the following on another thread last week:

There sort of wto schools od thought regarding this; one you could consider is like an old school view (to name it in some way) in which in general it is suggested to schedule your long ride on sat and your long run on sun and that way you'll teach your body to run on tired legs. The problem is that physiologically speaking that is not necessarely the case; while your body indeed might be recovering from a long ride and you'll carry some chronic fatigue by the time you do your long run the next day, also you most likely had the opportunity to refuel (eat) and rest hence it is not particular specific as running off the bike when your fuel storage has been already used.

OTOH, the newer view (again just naming it for the sake of the discussion) in general suggests that if you manage your training load over your schedule, then you'll have a better chance at doing more of it by spreading your more taxing sessions around allowing your body to recover from one to the next hence resulting in greater training quality. IOW if you do your long run mid-week by the time you train on Sat you most likely will be almost 100% recovered and able to traing more/harder. Also it frees up one day to ride more on Sunday, something important for IM.

I think both have a place in a training plan and as athletes you'll do whatever fits your schedule/needs better. IMO if you could use the 'old' school view early in the plan and during some specific week later on (i.e peak week) and use the 'new' school version when doing the greatest volume of training to fit more load and recover a bit faster. In the end, f you can only fit your long ride on sat and long run on sun or that's your preference or what works for you then go nuts, no need to change anything. OTOH if you struggle having quality sessions it might be worth considering a change. There are many ways to train for triathlons as we respond different...