Well if it's a curse then Madara should know about it right? Since he should be over 100 years old(well if my theory from kakuzu's age is correct) anyway, Madara is technically an immortal in some way. But I guess according to Kakuzu, there is no such thing as immortality.
*Hidan's immortality was limited, he needs to kill and perform the ritual in order to keep his immortality going.
*Kakuzu's was a jutsu in which he steals younger hearts before his others give out. But yet again his are limited since he needs to keep replacing them. As of Madara, I have no idea lol... but I don't think it's a curse since well, you could master all the types of Justu you ever want right? I think it would be more of a positive thing rather than a negative.
Nice theory though =]