Longest IM distances for each leg.

It depends on the individual--their background, base, the rest of their training.  In general, too many first timers (from what I see) get wrapped up in the distances of the long workouts.  Not focused enough on the consistency in training week after week.  You can't "make up" missing a half dozen 30-minute runs by doing a 3 hour run.

First time I needed to know I could do the distance so to speak...swam the distance in ows 2x, 100+ rides maybe 4-5 including 2 on the race course, ran 4 times 19+ miles. I remember one week I did long run of about 19 and long swim and for the first time knew in a deeper way yes I can do this.

I'm doing my second IM in 2 months  with a different coach and what I understand my longest rides will be 80 miles twice, 4-5 18 mile runs, and swims not sure. This time training I'm not always tired like I was last year.

Lots of different ways to train for IM and you need to trust your plan and not overthink things if possible

I consider myself in the 'experienced' group of folks. I didn't respond to the thread you were referring to b/c I took the question to be "what's the shortest long run to pull off an Ironman." Since my long run for an IM is 20+ miles, I didn't think I added anything to conversation. I, like you, enjoy the long run and think it's the most important workout leading to an IM.
To your question, I swim about 4500, bike around 115 and run 21-23 for my longest workouts leading up to the big day. My recommendation for first timers is get in enough that you feel confident on race day. Let the fear that you have work for you in your prep.

What JK said, in addition I think athletes/coaches often misunderstand setting a limit to a run workout due to diminishing returns. It is true that running posses greated strain/stress on our bodies and the ability to produce positive adaptations will also depend how well we can absorb the work done and recover from that session. When athletes are untrained it can take them longer to recover from a very long run (for them) and reach a point in which the negative results outweight the positive ones because their bodies are not trained to handle such load.

In general faster athletes can manage to cover longer distances in short durations of time and since our bodies know how long (duration) we have place certain strain on it and not how long we have gone (distance) then it is easy to see why fasties can run 20-22 milers and recover faster relatively speaking than a slower athlete. That's because the fast runner might cover the distance in 2-2:30 hrs while a slower runner might take 3 > hrs and the wear and tear that our body goes through during that time is the what each athlete/coach has to evaluate.

Of course intensity has to be considered and since a slower athlete will work at a lower rate the strain might be lesser, still given that begginner's bodies in general are untrained to handle such a load of work, then while the intensity won't induce as much strain on the body, the total load and inability to handle such load will. Ultra runners OTOH can handle bigger loads because their intensity is lower AND because they have trained their bodies to handle such load.

As JK said the sum of all your workouts will have a greater impact on your fitness level and race performance than 1 stand alone workout. Those big sessions tend to produce greater psychological benefits than physiological. For that reason it can be beneficial for a beginner and/or slower athlete to do a 3 hr run; not necessarely for the training adaptations from that session but for the confidence boots it can provide. The athlete will gain far more fitness from doing 30-60 min run 4+ a week, week after week for the 4-5 months training for IM.

In the end IMO it would be incorrect to state an athlete should limit his/her longest training run (or bike or swim) for an IM to x or y. I think the athlete (or coach) has to consider strenghts, weakenesses, limiters, fitness level, recovery rate, goals, etc and based on that decide what duration might work better in combination with all the training done before as preparation for the race. For some a long run of 1:30-2 hrs might be optimal while for others a 3 > hrs might be need it.

Same for bik/swim; usually since these sports place a lower amount of stress on our bodies hence we can handle completing the distances without having to invest as much time recovering as with running. Also because of this we can manage to handle the greater load of work even when our bodies are not optimal trained hence it is normal to increase the load on swim/bike a bit faster than with running. For that reason it is not surprising some athletes/coaches choose to strive completing the race distances through training. Still one should consider the athlete's strenghts/limiters and based on that define the training plan. A strong swimmer could get away by swimming less and maybe going the distance or not while an inexperienced swimmer probably should swim more and strive to go the distance (OWS specifically) at least once as a confidence boost and make sure he/she has the skills to cope with the challenge.

Good luck.