You have mastered the legendary techniques of Haagenti’s Divine Experiment. Your body no longer physically ages (although you continue to accrue mental bonuses), and you don’t die from old age. If you were middle-aged or older, your body returns to its prime— you retain your mental bonuses but lose any penalties to Strength, Dexterity, and Constitution gained from advanced age. Each day, when you perform your obedience, you create a small amount of mystic quicksilver; if mixed with a potion of cure serious wounds, it creates a dose of oil of life. Just like that created by a philosopher’s stone, if this oil is sprinkled over a dead body (a standard action), it revives the dead creature as per true resurrection. Alternatively, the quicksilver can be used to convert up to 1 pound of lead into gold (worth a maximum of 50 gp). This quicksilver loses its potency after 24 hours or when you next perform your obedience.
Because it says you stop aging I'd say that you don't immediately die. Death comes from a slow degradation, so pausing that degradation would preserve you. The way I'd rule it is that you'd return to the age you were before you started the obedience (or before the last time you took a break from doing it).
So if you started using this ability at 55, then kept doing it every day for 200 years, then stopped doing it you'd return to your 55 year old body (even though you were in your 26 year old body for those 200 years).
This is all likely GM fiat though.
Considering the fact that the source of this power is a Demon Lord it would be pretty appropriate to immediately turn to dust if you were to fail to pay your dues even once. I don't think there's a definitive ruling here so going with my or MrCharisma's interpretation is more up to which seems more interesting.
You'd start aging again until you performed your obedience. If you're an Indiana Jones fan, I'd modify it to age you one year each day you chose not to perform your obedience, per the Grail Knight.
I'd modify it to age you one year each day you chose not to perform your obedience, per the Grail Knight.
Oh I like this option. It gives you time to break out of jail or whatever so you can be obedient again, but gives you a ticking clock.
"If you were middle-aged or older, your body returns to its prime"
I'd say you're fine for a long time. Even if you age I would imagine it would be to whatever age you were when the boon first took place. Regardless the next time you do the obedience you would be restored to your prime.
Demon Lords may be A-holes but they also are probably keen on keeping their investments working for them. :)