The opener workouts (i.e. Truuli) are generally recommended.
For an Ironman: racing at Endurance, Tempo and rarely Sweet Spot, a few questions:
a. Is it better do one than not?
b. What day do you do it: Some plans have this 2 days out and others have it 1 day out?
c. Suggestion for specific workout for an Ironman?
With some suggestions I do plan on doing some trials of an opener workout before a long bike training ride to see how it goes.