Problems stand developing Tri-X at box speed.
Stand development with highly dilute Rodinal will indeed tame excessive contrast, as long as you agitate ONLY at the beginning - maybe lightly halfway through would also be fine. Agitating any more makes the process semi-stand, which won't get you a massive reduction in contrast, but only gives you that "walk away" convenience factor.
As for developers exhausting in solution, a good general rule to follow is that while liquid concentrates have in indefinite shelf life, diluted liquid developers must be mixed up right before use and used one-shot. Powdered developers mixed to full stock strength (e.g., D-76, XTOL) aren't quite indefinite, but last roughly a good six months or possibly more; but any diluted to a working strength (1+1, 1+3, etc.) must also be used one-shot.