A thought just came to me.....
Alot of you can probably agree that its hard to believe that Madara is still alive after all this time. Some of you find it hard to beleive that Madara is even Tobi and alive at all. Lets say for the hypothetically Madara is actually Tobi (which i highly believe to be so) HOW THE EFF IS HE STILL ALIVE?!?!
If you think about it the mystery of him still being alive isnt that great at all. We've seen a whole bunch of old characters with crazy ass life spans. Theres even a character who got his head chopped off and the dude was still alive!!
example 1: Orochimaru
Orochimaru is about the same age as Tsunade and Jairaya. Theres evidence that suggest that the Legendary Sannins are pretty old. I would guess maybe 50+? But Orochimaru like Tsuande looks pretty young and we know its because of the body transfer jutsu that he uses every 3 years in his attempt to never die so he can learn all the jutsu in the world.
My point being with this tech Orochimaru is practically immortal. He could live as long as he want just switch bodies every 3 years. "your not even human"- 3rd Hokage. Even though his soul or body is sealed and permenant genjutsu i think he could very well make a comeback. Kabuto said that his body could be seen as Orochimarus body and he has to fight as to not to be fully taken over by it.
example 2: Tsunade
I was going to use her but now thinking about it... Like i said shes old, 50+ i would have to guess but she looks like shes in her mid 20s. We have never seen her true form and we know she uses a jutsu or better yet her chakra to keep her self looking young all the time.
Point being even though her body is old she appears young. Ill get bakc to this later.
example 3: Kakuza
This dude was one of the oldest characters alive in the manga as he claim to have even fought the 1st (just like Madara). How was he able to stay alive for about 3 generations later?! (does that make him around 300 years old?!?) Well he steals his opponents hearts and by that i guess that prolongs his life. Theres no denying that his method, like Oro, practically made him immortal. Even the rest of Akatsuki called him and Hidan the Immortal Brothers or Immortal Team (correct me on the actual term. i just remember Immortal somthing). And speaking of Hidan.......
example 4: Hidan
This dude is the definition of immortal. We dont even know (at least i dont) what land or clan hes from and the source of his power but this dude cannot die!! Hidan- "I team up with him because hes the only person i cant kill". We saw his head get chopped off and it only annoyed him. We saw him get blown up and he was buried alive (literally) cursing up a storm. I doubt anybody knows why or how it was possible because the manga gave us little to no clue of the source of his powers or origin but that dude could not die.
With all that being said.. Madara could have used any of these methods to stay alive after his fight with the 1st. He could be using body transfer like Oro, maybe since hes sooo powerful he may have a great deal amount of strong chakra that would allow his lifespan to be greatly prolonged just like Tsunade's chakra keeps her looking young, maybe he collects hearts like Kakuza as well as collecting sharingans and rinnegans, or maybe he just have an unknown power to stay alive like Hidan. OOORRRR maybe his technique of staying alive thus far is something completely different and hasnt been shown to us yet.
Madara is the strongest Uchiha, power only rivaled by the 1st hokage who was the best of his time. The 1st hokage was strong enough to collect and tame Tailed Beast and he generously passed them around to the other countries like free bubble gum just so everybody had equal amount of power. He literally built the Hidden Leaf with his own two hands and the only person who rivaled him was Madara.
Madara whether you beleive he is Tobi or not is really strong and i think we take him very lightly. Alot of us dont beleive Tobi is Madara because we find it a little hard to believe that he could have lived so long but look at the examples i gave you. I think Madara is alive just because of his strength alone.