Lol, am I sensing some Thor/Norse mythology references? xD
So the fact that this is a dual layered genjutsu is already excellent. The first layer is kind of morbid, imagine watching oneself age at such an accelerated rate. However, most shinobi may deduce that this is a genjutsu quite easily, as aging in battle show very obvious signs and is physically impossible, allowing them to release it. They'd have to use a technique without handseals or some kind of full body surge. However, the second layer is where things can get pretty... "Loki" :snick:
I would use a fire technique if I note that my opponent has released the first genjutsu, and naturally, they will try to counter with water. However, the effect of this genjutsu will instead cause them to be hit by cold water/ice and subsequent numbness. This numbness opens them up to a final killing move.
Example scenario: I put an opponent under this Gen. He uses some kind of surge (hardening, nagashi or dojutsu/sensory etc) to break free of one layer, but then I follow up the gen with a Katon jutsu to make him reflexively counter with suiton. When he/she is numb from the ice water (lol, ice bucket challenge <_<) I can use that opportunity to kill them with high level earth or lightning.
Any insights about this jutsu that you have that would let me understand the tech better, -Best-?