Experimenting was one of Orochimaru's specialties. Ignoring his conscious was another.
Everyone knew he wanted to learn all the jutsu in the world; probably destroy Konoha while he was at it. But nobody ever knew why. He never told them.
He wanted to destroy Konoha, because Konoha would never truly let him go. He liked his home village, but he just wished they would let go of him; ever since Sarutobi let him go, ANBU and Hunter-nin have been dogging him. Orochimaru wanted peace, and Konoha wouldn't let him have it.
The purpose of his experiments was to find a way to protect those he loved.
He never told anyone, but he too, loved someone. He wanted to show her everything, make her strong, so she could protect herself. He developed the Curse Seal to give her strength. And then… and then she left him. Orochimaru couldn't really take it. Without her, Orochimaru's work was for naught. The one person he loved betrayed him.
Orochimaru threw himself at his experiments then. Immortality… He reached for the heavens themselves. He hoped that with all eternity, his heart would heal.
The Sharingan was something everyone knew he desired. Orochimaru wanted to learn all the jutsu in the world; what better way then to copy them? With all the jutsu, when he finally found another person to love, he could pass them on, every single one of them. And then they would grow strong. He would give them the Ten no Juin, to further increase their power.
He had refined the Ten no Juin. He refined it so much, he eliminated the dark urges; the desire for power. He eliminated the slow, insanity it would bring them without the drug; he eliminated most of the dangerous effects of the level two. He wanted his special person, to be able to use the power easily, without risk.
Orochimaru was still searching for a precious person. But then again… He had all eternity, had he not?